People don't want to live on top of one another. We have a huge country, and we enjoy having our own land. I understand most people in this world don't understand that rationalization, but it is what it is. Murica.
Do you have any sort of proof that this happens on any sort of statistically significant basis? It appears most of the people in this country live in urban places and that this has been an upward trend for a long time...https://en.wikipedia.org/wiki/Urbanization_in_the_United_Sta...
Apparently most of America, wants to. Your observation doesn't really mean a whole lot, I could move to Michigan and buy a 10 acre lot for a tenth of what I'd pay here in king county, but I and most of the people that live here don't want to do that....and not only is this my observation - it's a statistical fact.
The last decade has seen people leaving rural areas with their own land to very much live on top of one another in the cities. More Muricans live on top of one another than you're giving credit for. In the context of this thread, no one is suggesting building subways in the middle of Wyoming - this conversation is very much focused on urban areas.