You just sound like you like to "people watch" which is cool.. I've never really been a people watcher kind of guy.. In fact, I tend to stay away from crowds and people as much as I can, unless I'm doing a show or something - then I'm a total ham and want to talk to an interact with everyone..
Interesting theory on people getting all up in your grill.. My theory/guess would be similar, but not as complicated.. People from New York or other busy areas are probably used to be crammed up against each other in subways and whatnot, so they're used to having their spaces invaded and invading other people's spaces and its no big deal..
Whereas in my tiny hometown, or other smaller areas, if someone gets within 2-3 feet of me, I'd ask if I could help them and I'd probably back up to re-create the space between us.. We're not used to people touching us or being within 3 feet of us.. So, we're weird!
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..