I think, honestly, it's a part of growing up - much as I hate to use that term.

If it weren't for things like Snapchat and such...Well, let's just say that once in high school I forgot to talk to a friend for so long he thought I was ignoring him. With my friends I can be very "out of sight, out of mind." Doesn't mean I'm not close with them, but it takes more conscious effort on my part to think of and involve my friends than I guess is typical.

The plus side of hanging out with friends less (and as you may remember I do tend to "go out" pretty often) is that you have more time to develop your own interests and hobbies. I think that's valuable. As people age they develop things that cause them to be free less, and as all your friends develop more of those commitments (like significant other, family, houses, etc), it means that even if you're free, they might not be. So you get more spare time to yourself, and I think people start to develop the habit of seeing spare time and using it for themselves as opposed to immediately reaching out all the time.

I don't know, it's crackpot wisdom from a 25-year-old. Might be talking out my ass. But I agree with you: just because I don't talk to someone doesn't mean I am not close with them. I'm also a completely terrible pen-paller and email-er. Lack of physical proximity diminishes the urgency to keep conversation going. Unless, like I said, it's going on right there in my hand and I can get back to it quickly.