This is a very interesting topic, and one that really has no end of arguments. I'll weigh in here as a father of 4, step-father of 2, and grandfather of 4. So I've seen my share of kids growing up on bikes. And lots of that done on box store bikes. First, not everything Wal Mart (insert your favorite hated box store instead) is complete junk. But a lot of it is. Assembly is another issue. Around here, it appears store are using employees to assemble, rather than a third party. So it's hit-and-miss on proper assembly around here.
When it comes to kid's bikes, longevity isn't all that much of a factor, as I've found the kids outgrow them before they wear them out. Keeping in mind that where I am, you really have only about 6 months riding season for most people. My kids all started on box store bikes that were more than reliable. In fact, my shed is home to a $25 BMX purchased on clearance at Wal Mart 12 years ago, for my youngest son. It's still rideable, the only thing I had to do was continually replace the rear tire once he discovered he could leave long black marks everywhere he went. My oldest daughter did her second 100km ride at the age of 10 on a BS bike (first was a year earlier on an old single speed 24" wheel coaster brake Glider, but that's a different story).
As my kids grew older, they went through both BS and LBS bikes. Many times I found LBS bikes spec'd the same as BS bikes for double the price. Yeah, the stickers on the frames were different, but that was it. And yes, I have to go through the BS bikes and set them up correctly. But $150 for a 20" CCM mountain bike at a box store and $300 for a Bonelli that was the same damned bike from the LBS, guess what I bought. Not all them were BS bikes, if I came found a deal within say 20% of the BS price at the LBS, I went LBS.
There are probably a million kids out there riding around on cheap BS bikes. I hear all the talk about kids getting hurt, bikes only lasting a month, etc. But what are the numbers on that? The real numbers, not someone just guessing because they don't like BS bikes or their kid trashed one. Real numbers. Without them, you're just playing Don Quixote. Prove to me how bad these bikes are. Show me that we need to demand these stop being sold. There are lots of kids growing up poor that would not be cyclists without a BS bike to start with. I'd bet many kids wouldn't know the thrill of owning a new bike (or any bike) if BS bikes didn't exist. And if you can't get them on a bike as a kid, it's pretty hard to get them on one as an adult.
Rather than try to control what box stores sell (we have far too many rules, regulations, restrictions and other controls in our lives today), perhaps the better choice is to set a required checklist when a bike is sold, to ensure the store is setting them up correctly. And perhaps requiring a notice to given if a bike has parts that cannot be replaced (I've yet to see a bike with parts that can't be at least substituted, but they may exist). And let the consumer decide what they want. If we demand the end of short-lived bicycles, where do we stop? Our lives are filled with disposable items that we readily buy up as quick as we can. The reality is that most items CAN be repaired. It's just more cost effective to buy a new one. Bicycles are just one item in the very long list.
I get that there are no shortage of people out there that hate BS bikes. And probably with good reason. But not everyone can afford to drive a Volvo. That's why Daewoo exists. They aren't as safe, and they don't last as long. But they get the job done at a fraction of the price.
What bugs me the most is the *****mongering of the brand names.