Can I offer up one more possible contributor? Maybe it's cliche, but car dependency. I have family and friends in my own medium-sized city, but the thought of driving all the way over there (20 minutes - 1 hour, totally random), or, even worse, forcing them to drive all the way over here by the invitation, is a bit much. Driving home, even worse. You wanna have some drinks (maybe more than "some", lol), but you gotta drive home.

I know in the 70s folks were just as, if not more car dependent, but it kinda worked back then. I only have real experience in the 90s, but even then, I remember my parents having people over, and I never got the impression they came from very far. Sometimes blocks away. They still drove... but it wasn't the same.