I thought I drank because I enjoyed the feeling it gave me. With hindsight, I'm not so sure. What I do know is that, in the end, I drank because I drank and that's what I did.
I don't think, apart from the first couple of times at uni that I drank to be sociable, or to be with people. And after that, I tried to be with other people who drank like me, I guess. Or people who didn't drink if I was away from it for a while. It made it more acceptable. Not to me, as such, since I've always drunk on my own as well, but... generally.