counter-argument: by not having to appeal to (most) families, big cities can focus on attracting young professionals, hence the original moniker: YUPpies.
But RTO is still contentious, and the ability to find a job if I moved to vaguely-near-Boise would be terrible. One misstep at work, or even just another economic shift, and I'm moving again.
But I'd love to be in a smaller city. Annapolis MD, or coastal WA or deep mountains MT, whatever.
And I know several parents who tried the "go it alone" method for a while, but eventually decided to move back to one of their hometowns, specifically to be closer to their parents for reasons related to their kids. Most of it seems to be a mix of wanting nearby, reliable childcare, as well as just wanting their kids to grow up with regular contact with their grandparents. (I've also seen the phenomenon where the grandparents, after retirement, end up moving to the parents' location, but often that requires the grandparents to move to a higher cost-of-living area, so I expect that happens less often.)
I don't plan to have kids, so this is certainly a grain-of-salt-worthy opinion, but it feels to me that parent-marriages would be on average healthier if the parents had easier childcare options so they can more often do "date night" type things. Certainly nearby grandparents is not the only way to achieve that, but it is one of the simplest options, assuming grandparents who are happy to be involved to that degree.
First, the states with the big cities they moved to also have smaller towns outside those cities that are fine for families. They can move to one of those and still have sufficient contact with the city to maintain their career.
Second, their spouse likely is not from the same state they are from, and may not want to move to that state. And they may not want to move to where the spouse is from.