Absolutely nothing is wrong with them.
I've heard the typical: ' you know that I wouldn't be caught dead on a Schwinn ' since 1975.
Back in '75, it was more a reaction to Schwinn dealers' arrogance and the factual knowledge that for the money , there were indeed much lighter, high quality road bikes with Japanese components (Maeda-SUNTOUR or SHIMANO) that were in the marketplace then that were priced better than Schwinns and thus for the dollars spent, if you knew where to look and what to look for, you did substantially better than shopping at the Schwinn dealership where prices were rigid and high.
You had to have been alive them, to grasp just how it was.
Inflation was significant by 1975 and remained high until well into the early eighties.
Anyone remember the WIN buttons? Everybody remembers the Yellow Smiley face.
Schwinn built quality bicycles. Columbia, Ross, Huffy, and AMF built bicycles too.
The Ashtabula One-Piece crank or AMERICAN STYLE crank as it was known was a fixture of millions of bicycles.
It was unbreakeable, easy to service, supremely reliable and simple.
There is a fantastic book that everybody that owns any basic bicycle, or any road bike made before 1980 should own a copy of.
The book is " GLENN'S COMPLETE BICYCLE MANUAL" (c) 1973 339 pages 8.5 x 11 softbound --by CLARENCE W. COLES and HAROLD T GLENN
This book probably sold over half a million copies during the period of 1973 - 1977.
This is the best bicycle book that has ever been written. Many people still share that opinion.
The first chapter of GLENN'S COMPLETE.... is called The Bicycle and You - CHOOSING YOUR BICYCLE , and for the for the first time ever, folks were told in explicit detail all about bicycles made in the USA versus the more advanced European makes at that point in time circa 1972-73.
There is no specific mention of Japanese bicycles (Fuji / Bridgestone....) or others with SUNTOUR or SHIMANO components as at the time the book was written there was the belief by the authors that Campagnolo equipment was the world's best. This was what everyone thought at the time, having no experience with maeda SUNTOUR or SHIMANO or just limited experience in knowing they were on inexpensive bikes just beginning to arrive.
In the chapters that cover adjustment/removal/replacement of REAR DERAILLEUR both the Suntour and Shimano are praised as quality and covered with the section.
From page 6 (...choosing your bicycle) (c) 1973 Glenn's Complete Bicycle Manual : "For the individual purchasing his first quality-built bike, here are names that indicate better component parts on bicycles in the price range indicated, but the list should not be considered all-inclusive. At the derailleur units, the names of Simplex Prestige, Huret-Alvit, Campagnolo Gran Sport, and Campagnolo Gran Turismo are found on bikes in the $100 to $250 bracket. The Italian firm of Campagnolo dominates the market of bikes costing over $250 with their Campagnolo Record and Campagnolo Nuovo Record units"
This great book is the book that really informed millions of Americans as to the various distinctions between bicycles, especially road bicycles that to the untrained observer in 1972 -1973 probably looked all alike...........you just thought, oh yeah that is just another ten speed..................Well the authors, Mr Coles and Mr. Glenn tell us about luggged frames, double butted joints (not the kind hippies were smokin in '72..) and Reynolds 531 tubing and details on how a higher quality frame differs from something common and inexpensive. From page 6 : " The frame on bicycles under $100 are mass-produced with the tube members butt-welded at the joints. They are heavier built to withstand the rough treatment of city riding".
My belief is that many baby boomers like me first came to really learn about such differences from reading the GLENN'S MANUAL in the early to mid Seventies.
I recall CONSUMER REPORTS did some comparison/testing of 10 SPEED ROAD BIKES back at that time too. If I recall acurately, there was one that I remember buying and reading back then, the JANUARY 1974 Consumer Reports Issue on TEN SPEED BICYCLES.
Basically that was it for me as a young adult then, although I am sure some people that were more tuned-in were probably reading specific Bicycling magazine or related publications. The GLENN'S MANUAL and CONSUMER REPORTS were what really told millions of us "BOOMERS" that maybe the bicycles that we thought were just all ten speeds were not all the same. By 1975 the average Boomer that was already gainfully employed and fresh out of college, that wanted a nice bicycle wanted that bike to be light and high quality. Forty pounds of electro-forged Schwinn and the One-Piece crank was in a sense as desireable to them as a 1965 Corvair convertible was. Pretty in appearance but undesireable because of the heavy weight of the Schwinn.......the Corvair was perceived junk because it was notoriously unreliable, much like it's successor the VEGA.
Every one who wanted a ten speed bicycle by 1976, wanted something LIGHT because there were so many that were about 30 pounds on the market at that time and several in the 26 to 30 pound range. It was the trend and what folks that knew about bikes wanted to buy.
It is not all bad, having added weight, a super strong frame , and an Ashtabula ONE-PIECE Crank , but it definitely was not something that most Roadies (not the folks who work for McCartney or the Stones..) would have by 1976 or 1977.
Another factor at play is that because the ONE-PIECE Crank is so durable and simple to service, so many of these ancient TEN SPEEDS, FIVE SPEEDS, THREE SPEEDS, and SINGLE SPEED bicycles still survive.
Many bicycle shops today HATE THIS, that any one with the GLENNS MANUAL and basic tools can revive an old bike that has been in the shed, attic, barn, garage, basement, or found at the dump. They would rather sell you something for $550 than to see you rolling around on an old Huffy, Columbia, Ross, or Schwinn. Many folks online that have intense hatred for such old bicycles and raging hatred for new Wal-mart / Target bicycles from China, may work in a Bicycle shop, or perhaps own a local bicycle shop. They view that as an attack on their livelyhood as more folks riding Walmart /Target bikes or old bikes means that other people will see that you can get around the neighborhood or ride anywhere on a $120 sale special from Walmart or Target or something dragged out of Aunt Judy's garage. They don't view it as more folks riding bicycles = more probable future customers. They view it as oh damn, there riding those POS bikes instead of the $550 bikes that my bike shop sells. Some bike shops (you know the ones....) severely detest having any "common" bike come in the door, as it is potential sign to customers inside there that there are bicycles that can be purchased and ridden for far less than the $1800 sticker price that they may be in the process of being shown.
Because millions of Bike Boom Era (1971 through 1974) bicycles still survive, as well as many excellent, well kept examples of late seventies, eighties, and nineties models, one can pick up one for next to nothing in cost. Thus, they have to be creative and market their bike shop offerings as vastly superior, which they likely are, but what they don't tell you is that not everybody needs the vastly superior equipment in road bike forum. At its basic forum, a bicycle is just a bicycle and it does not have to be complex. Even a $89 Wal-mart special coaster brake single speed can provide enjoyment and good exercise for someone.
Just like you don't need a weatherman to know which way the wind blows, you ain't got to buy a fancy smancy bicycle from your local bike shop.
Walmart / Target /Amazon/ Webland all have them. It depends on just what exactly that you might be perfectly satisfied with.
A bike from a local bike shop will be properly assembled, properly adjusted and perfectly ready to ride. If you go the other route, NEW or Old used, you will have to determine if the bike is ready to ride, or you may have to assemble it and/or fine tune it......unless you want to pay the LBS to do it.
Nothing is wrong with the ONE PIECE CRANK or any old bicycle.
There are thousands of folks that restore and drive Corvair Convertibles and MGB's. Both cars were mostly POS as originally sold, but there are enough "solutions" that those faithful to those cars have figured out over the years that they can be driven with a degree of reliability that did not exist in the old days.
One certainly cannot say that the '65 Corvair convertible, or a '73 MGB is not a very attractive car with a nice ride. Many folks will say oh why bother with such trash but you know those things will turn more heads today than they did back in the day because of their timeless look and because most folks have never seen one up close and in person. That sort of adds to the "Cool Factor" doesn't it even if most folks find them undesireable.
It is the same thing with a Murray, Columbia, Huffy, AMF, Hawthorne, Hiawatha, Western Flyer, Flying-O, Free Spirit, Ross, Rollfast, JC Higgins, JC Penney or K-mart special, Schwinn or whatever bicycle that may have the ONE PIECE CRANK.
If you like it, enjoy the bicycle and ride it proudly and don't hesistate to tell others how many miles you have ridden it and for how many years you have ridden it.
It obviously is a decent bicycle that has served you well. Just realize that just as you don't need a Ferrari for your everyday automobile......