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.