Hasn't it always been a thing, though?
I'm sorry for people whose family is not in a position to, or chooses not to, help them, but I think it's always been pretty common (albeit not universal) for parents to support their offspring.
Until the 2010s, it was fairly socially expected that you'd move out of your parents house at 18 and either find a job or go to college, and do all that on your own dime.
It was always a weird concept for me coming from an immigrant family where we all pitch in together to help each other, but a relatively large minority of Americans (maybe 15-20% actively chose not to) and a large majority (maybe 20-30%) didn't have the means to.
If you're in your 20s-30s, best case your grandparents grew up in the 1950s-60s - which absolutely wasn't a walk in the park, but the average American was miles away the richest person on the planet back then, and the "nuclear" family was the structure of choice (that's why it's called the nuclear family - 1950s techno-optimism a la Fallout)
On the other hand, if your family immigrated then the familial ties based system continued to exist.
>Hasn't it always been a thing, though?
Family size is a factor.