Of the communities mentioned that I recognized, most were retirement-aged communities. In that case, wouldn't age demographics alone explain the population differences?

Many of those cities are hot, possibly short of water, and offer a far different cultural environment than SF. Not having kids, I don’t know what areas are good/bad for kids, but they’d have to have money and the willingness to spend it to have good schools. To me, there are things more important in money that determine where to live.

Soon to find that the only economic opportunities are in cities. The half assed infrastructure that is new today might last 20 years. Then they will find themselves flowing back into cities.