I think that's the wrong way of looking at it.

In the past, when proximity was the biggest thing, we'd look to invest more in the people proximate to us.

They like something I don't? Okay, fine, I'll do it, so I have a friend. And vice versa. I may not really care about doing X, but it's a way to connect.

Now? Now we are willing to keep looking. We want perfect friends. We are less willing to invest time in people nothing like ourselves, because it's comparatively easy to find others.

Even as i kid, I remember friendships that were basically "This kid is in my neighborhood" or "This kid's parents go to the same church as my parents", and that was it. Oh, they liked to rollerblade? Okay, I guess I'll learn to do that. I like video games; they'd learn to like that. Etc.

Now? Now it's superhard; even places I'm proximate to others, why would I choose to spend time with them outside of the one activity that brings us in proximity?