You also get to hang out with a bunch of people doing similar things. You compete with them; you learn from them; you learn by teaching them.
You get to talk to people who have done important things in the field you're working in.
Of course, this is all in the ideal situation. Unfortunately modern education seems, for many people, to be "cram 'em in to get the funding". The education is secondary. Certainly some universities in the UK appear to be just extensions of 6th form education, and not the launchpad into proper academic rigorousness that they should be. (Not all, obviously. There's a lot of great work coming out of uni's.)