Believe it or not, there are supposedly intelligent people out there who think the internet will replace universities.1 It didn't take Sean Caroll very long to come up with some excelent reasons why this ain't gonna happen [Will the Internet Replace Universities?].
Let me add one more—research experience. You can't learn what it's like to work in a research lab if you're sitting at your desk in the suburbs.
Why do I get the feeling that most people don't understand what a university is supposed to be like? Is it true that most people think of universities just as places where you come and listen to lectures and then go home?
1. Back in 1970 their parents were convinced that television would mean the end of universities as we know them.