That's my experience in cities, but I don't see it tied to affluence.
I do see a tie to perceived threat - people who feel they are in danger don't want to risk interactions. First, a rule of the street is, 'don't get involved'. Second, you don't know if the person next to you is crazy.
But few places are that dangerous; if you do get to interact, the only varient seems to be the seemingly arbitrary subculture of that particular neighborhood.
I do see a tie to perceived threat - people who feel they are in danger don't want to risk interactions. First, a rule of the street is, 'don't get involved'. Second, you don't know if the person next to you is crazy.
But few places are that dangerous; if you do get to interact, the only varient seems to be the seemingly arbitrary subculture of that particular neighborhood.