Ok this is a super fascinating intersection of American social history
So the first thing you have to always keep in mind when thinking about Americans and their behavior is that the country was founded by people so absurdly religious that the British kicked them out. Then, along with some wealthy land owners, they said "fuck off" right back to the crown, declared "no take-backs", and went on about 100 years of aggressive westward expansion.
If you're not familiar with the phrase "manifest destiny" it's worth looking up. It's fundamental to American society
Fast forward a bit to post-WWII and the economic boom of the time. "The American Dream" - and the promise to our returning soldiers - was owning your own house with a yard, wife, kids, dog, and a car. And given our history, and the return of thousands and thousands of young men from the war, that kinda became the measuring stick of basic success: moving out.
And of course since America is the land of opportunity, if you can't do even that much, you've only got yourself to blame /s
We all know the meme of "striking out on your own" as a symbol of maturity. This is just what happens when "striking out on your own" becomes a cultural identity