I do know that I've lost contact with most of my old friends/crowd and have found nothing that really "pulls" me towards most of my coworkers, PTO/PTA members, church group members, etc, that would want me to pursue any deep friendships beyond that of acquaintance. I have my child and that seems to be all I really need at this point in time. Do I enjoy going out? In small groups or one-on-one, yes I do enjoy it-but not on a regular basis. I'd prefer to be at home over going to a party. Fifteen years ago I would have had a much different answer. I've also noticed that when I do go out I prefer the events to be more staid, such as a lecture, a local band concert, a small town play, etc. I don't want to go into anything too noisy.
Nowadays I prefer quiet time, reading books, working on jigsaw puzzles, crafting, and other things. I like long walks with the dog instead of hanging out with a group of people. And if I had enough money I'd prefer to own a small acreage outside of town, where I could raise most of my own produce, maybe have a couple of goats for company, and learn how to become ever more self-sufficient.
Does that make me a loner? I don't know. Most of my coworkers think it makes me a bit crazy, since I don't like going to bars and partying all weekend.