Economists hate this one weird trick!

I mean I guess they get some perceived value out of the rims that makes the stability trade off worth it.

Whatever you put aside is not going to be enough to prevent complete financial ruin if shit hits the fan. You might be able to cover smaller emergencies like an appliance breaking or your car needing repairs but literally just giving birth or being in an accident can bankrupt you in the US. I'm not at all surprised low to medium income Americans would just give up and accept their inevitable financial ruin instead of trying to be maximally frugal and socially ostracize yourself, forego most forms of entertainment/recreation and still not be able to get out of survival mode.

Desperation is a good motivator - but not for rational actions. It triggers our survival instincts: hoard what you can, feed on what you can get, grow fat, make rash decisions. This is what the modern economy is built on. FOMO, impulse shopping, conspicuous consumption, high calorie fast food, deals and discounts on overpriced goods, planned obsolescence, etc. We need consumers to be perpetually desperate and starving. Credit just means we can circumvent Henry Ford's problem of them not being able to afford to buy anything because they still can't afford it but are able to pay for it until their credit line runs out.

People need to stop moving out of their parent's house if they can't be stable. That's the root cause of a lot of the problems in the US.

We need to change money flows and redistribute wealth so people can have a hope of saving some money, because they actually can make more money than they absolutely need.

And then you have the same people complaining about low birth rates...

Does living independently before you get married make you more or less likely to have kids? That would be an interesting statistic.

This assumes, among other things, that they come from a stable home that has space for them and access to the things they need to create and maintain an income stream.

If you look at the home ownership rates of that generation it would be a fair assumption

For the entire population, sure. For a subpopulation that doesn't have a stable income, not necessarily, particularly given class mobility statistics.

This is now happening.