I'm not sure "become socialized" and "make friends" are synonymous. There's a lot to learn about interacting with other people, and cultural norms and expectations, and so on, even if you don't especially like the particular other people in question.

I'm also tempted to say that for me, at least, the fact that I tend to ignore/edit out a lot of the people around me means that I benefit from being in proximity to a largeish number of people, just so I have a chance of bumping up against the couple I can bond with. If I stayed home, I wouldn't make any friends at all. (But I'm not actually sure how well this logic would hold up to a controlled experiment. :) )

One thing that I have noticed about school, for me, was that I learned a bunch of stuff that I'm glad to have learned, but it wouldn't have occured to me to learn about if someone hadn't put it in front of me. I suspect socialization's a little like that, too.

(But then, I went to a wierd school that was well-suited to my particular needs, and gave a lot of individual freedom compared with most people's that I know.)