Where does this meme come from? As a young person man, I have no debt, no kids, no elderly parents to support, and so on. Since I'm in software development and didn't try to make it in SV, I had enough cash to cover multiple years of living expenses after about a year of working. Hell, even just collecting unemployment would cover my living expenses. Entry level jobs are plentiful, while my understanding is that senior dev and management jobs are harder to find.

I've only been at one job so far, but my opinion was that I would suffer literally zero short-term effects for getting fired/laid off. I probably would just end up at a better job since I've got a bigger network and time to spend grinding out interviews if that happened.

So in the end my employers would act the way you described, but I would be confused about how to respond to them as they had zero objective leverage over me. As a result I could pretty much just work a regular 40 hours and my boss could just blow smoke out his ears if he didn't like it.

As an aside I actually don't have an issue working extra hours sometimes, but 100% of the time I'd been asked to, I thought it management was responsible via poor planning or making shitty technical choices. I'm fine helping out to cover someone else's bad work, but people would just become more rude/demanding. So I would just stop since I was only working extra out of kindness in the first place.