Connections basically. I'd argue that is the main benefit of college.

You can of course study and learn the academics of it all largely on your own if you want. But the main benefit of college is that you've got a lot of other people around who share your interests, or don't and force you to expand your understanding of the world. Then later hopefully if you're socially competent you're gonna have potentially beneficial career connections.

Which is ironically why going to college to party isn't actually a bad idea. Just need to learn to balance it all.