There's a massive appetite for questionably manufactured goods today, and one thing I have noticed is that where today's "retro" bikes use steel parts, it's often really soft and crudely formed and finished steel.
I went through a big box store Schwinn for a family member because it was having problems. This was a utility type bike that was white and green (had fenders; chain guard; etc.). I don't recall the model name, but it was like a $200 bike, at least that's what I was told. It was actually reasonably attractive. But mechanically, it was not good. The tolerances were very loose; the bearing races were not properly hardened; and there was not enough grease in the bearings anywhere. Stamped steel parts were under-built and very soft. Sprocket and cog teeth wore quickly. The chain was of a basic, indifferent quality. The bottom bracket cups rattled around due to a very loose fit. The headset never seemed to be right - either it would bind or the fork would be loose. Some tolerance there was off as well, but eventually it was made passable. After one year of use, the bottom bracket cups had gouges. None of the bearing cage assemblies could be re-used - too cheap and too badly set up.
I guess what this adds up to is that there's this whole underbelly of "retro" bikes of all different brands that came onto the market, but that were bicycles in appearance only. There was no attention to properly hardening the right surfaces, or of manufacturing sufficiently sturdy steel parts. There was no attempt to get tolerances right. In some cases, I've seen bikes in big box stores where bars and cranks are noticeably bent, even to the naked eye... and these are supposed to be new bikes. There was not enough know-how in the store for a proper set up, and the product itself was not properly manufactured to start with.
A basic, 1970s era Chicago Schwinn usually had at least correct manufacturing techniques and decent quality on it. They were heavy and largely obsolete in some ways, but I will say they were well-made and tended to be very durable. The stuff people are getting sold now as "new retro" type bikes in the big box stores aren't even close to that, let alone a 1940s or 50s era Schwinn when quality and features were much better than in later years. My relative should have spent $100 or $150 on a basic 1970s Schwinn 3-speed and all the needed tune-up parts rather than $200 on a new big box Schwinn. With proper maintenance you might be able to get that 1970s Schwinn to last a lifetime, and that certainly will not happen for the big box bike I was stuck fooling with.