Because US cities became slums, and rich people lived in the suburbs. In the rest of the world the rich people live in the cities and the poor people live in the suburbs with long commutes, there is no reason USA can't work like that as well.

Except that the US has the space and many/most people don't choose to do so--at least full-time.

Even in places where the wealthy had to live in the city, they often had summer places (in particular) elsewhere.

If you don't need to live in a city, for a lot of people (including myself), it makes a lot of sense to live elsewhere and go in for things.

I could live in a city but I have no particular reason I have to. So I choose not to at this point in time. Which is true of most of my friends as well.