I almost feel as though suburban living forces this in the modern era... the area my parents moved to when they left the small town where I was born to for the sake of raising children with cul-de-sac and good school district had almost nothing to offer for me as a young adult, so I left and moved across the country to a place which was more in line with what I was looking for. There were few jobs nearby in my chosen field (or really any field for an educated young professional, service industries dominated) so my peers all left, too.
We've chosen hyper-specialization of our living areas. The places which are good for raising children are mostly horrible for careers and social life. The places where young people can get ahead and be social aren't as traditionally convenient for raising children (unless you have lots of money).
You pretty much have to pick where you live based on what phase of your life you're in, and I think for most people the expectation is still that once you get married you'll just move out to the 'burbs. Personally, I hate the idea, but I'm both not in a place in life where I'm too worried about children and also fortunate to work in an industry where its at least theoretically viable to afford to raise city kids and maintain a career.
My parents are getting ready to retire and thinking of moving to the mountains somewhere because being retired is no fun in a place where everything is optimized around children and everything is developed family-size. They won't be a support system where they are for my hypothetical kids anyways, and are eager to escape the suburb I grew up in as it has declined over the decades, so I wouldn't want to be there either.
Wrapping up that rant... quite simply, I insisted on moving away from where I grew up because there was nothing for me there and I wouldn't want my kids to grow up in that place. The fact that my parents still live there for now is mostly incidental. (But I also generally think suburbs are a worst-of-both-worlds kind of thing, none of the cohesive culture or community of a small town but also none of the variety, walk/bikeability, or cultural diversity of big cities, so my bias might be showing).
Another major factor you didn't mention is urban housing prices. Before kids, we lived near downtown Seattle in a walkable, urban neighborhood. It was great, and is where I would have preferred to stay long-term. When we decided to have kids, we knew that buying a large condo or decent-sized detached home within the Seattle city limits would be way out of our price range (housing prices in Seattle have almost reached San Francisco/Silicon Valley level).
So we moved out to the burbs, where we could afford a starter home big enough for our two kids and a mother-in-law.
Maybe a contributing factor is that it is significantly easier and more acceptable to move house in America. Thinking back to where I grew up, the house we lived in was where my grand-grand-parents were born; it would be pretty much unthinkable to move (and was not even possible in previous non-capitalist regimes) so people stick around in close-knit communities. But maybe if moving was dead-easy like in the States this would naturally fall apart?
I guess it's already happening to some extent with Schengen and young talented engineers moving to job centers.
We've chosen hyper-specialization of our living areas. The places which are good for raising children are mostly horrible for careers and social life. The places where young people can get ahead and be social aren't as traditionally convenient for raising children (unless you have lots of money).
You pretty much have to pick where you live based on what phase of your life you're in, and I think for most people the expectation is still that once you get married you'll just move out to the 'burbs. Personally, I hate the idea, but I'm both not in a place in life where I'm too worried about children and also fortunate to work in an industry where its at least theoretically viable to afford to raise city kids and maintain a career.
My parents are getting ready to retire and thinking of moving to the mountains somewhere because being retired is no fun in a place where everything is optimized around children and everything is developed family-size. They won't be a support system where they are for my hypothetical kids anyways, and are eager to escape the suburb I grew up in as it has declined over the decades, so I wouldn't want to be there either.
Wrapping up that rant... quite simply, I insisted on moving away from where I grew up because there was nothing for me there and I wouldn't want my kids to grow up in that place. The fact that my parents still live there for now is mostly incidental. (But I also generally think suburbs are a worst-of-both-worlds kind of thing, none of the cohesive culture or community of a small town but also none of the variety, walk/bikeability, or cultural diversity of big cities, so my bias might be showing).