The notion of pre-boom bicycles being"gas pipe" is somewhat exaggerated, though not unfounded. The first great bicycle boom occurred in the 1890s and the USA was at the forefront. Bicycle evolution was staggering during this period. Developing metallurgy led to stronger and lighter bicycles. Manufacturers were experimenting with new steel alloys and there were even aluminum frames, aluminum rims and aluminum components. High grade competition bicycles were routinely sub-20 lbs by the start of the 20th century, though these were still single speed, fixed gear.
However, the "boom" attracted more manufacturers to the industry and the increased competition led to a downward spiral in prices and market saturation, at least in Canada and the USA. By the very late 1890s, the boom was bust and many manufacturers went bankrupt or amalgamated. With the industry in jeopardy. the USA government stepped in and imposed heavy tariffs to protect the remaining USA manufacturers.
The industry recession in the wake of the bust all but killed off the high grade, adult bicycle in the USA market. Most consumers had taken advantage of the deflated prices and were not in need of a new bicycle. The industry initially tried to stir interest with a new "chainless" (i.e.. shaft drive) models but that failed. With consumer interest at a low and tariffs effectively keeping European developments out of the country, the remaining manufacturers, to a large extent, lost interest in further technological development. The manufacturers settled into a rut of inexpensive, low cost, heavy, coaster brake, roadsters.
The problem was compounded by early 20th century developments in the automobile. As automobile prices decreased, their sales increased, to the detriment of adult bicycle sales. By the Great War, the USA bicycle industry was primarily a children's market. The significant market development during the Great War was the male juvenile's interest in motorcycles. This prompted a cosmetic "Motorbike" era, which prompted manufacturers to add truss forks, double top tubes, faux gas tanks and other features to reflect motorcycle styling. The weight of bicycles ballooned under the influence.
The government tariffs started to ease after World War II. The first beneficiary was England, who was granted progressive relief in order to rebuild her bicycle industry and pay off war debts to the USA. This resulted in a post war influx of British 3 speeds and established companies like Raleigh in the USA. American servicemen had become familiar with the advantages of internally gears hubs while stationed in Britain during the war and provided a ready market after the war.
Tariffs for other countries started diminishing in the 1960s, leading to import of various European manufacturers and for many Americans, their first exposure to high grade, derailleur equipped bicycles. When the baby boomers outgrew their 1960s hi-riser bicycle and were looking for something new and exciting in the early 1970s, the "10 speed" was the obvious choice.
So, while butted, manganese-molybdenum, and chromium-molybdenum tubesets and derailleur bicycles go back several decades prior the ealy 1970s boom, they were largely unknown and unavailable in the USA, due to a disinterested industry that was protected by heavy tariffs. As the tariffs eased, European developments started appearing in the USA and USA manufacturers took note and followed suit. However, for over a half century, the USA industry was dominated by the heavy, coaster brake, roadster.