Socialization is qualitatively very different when you live in the same building as people who share your interests. Without this, every meeting has to be planned days in advance, and bootstrapping a friendship to the point where people are even willing to make plans with you is a huge hassle. I found this feature of college extremely valuable and many others do as well, even if you would not. (It's true that this is really a feature of dorms, and classes themselves don't help much with meeting people, but it's still part of the experience, and how else are you going to concentrate hundreds of smart STEM-interested people into one or two city blocks?)