I know an english major who graduated still unable to distinguish between "your" and "you're." Who would you rather have in college, her or me?
Well, she apparently needs further education more than you do!
Someone pays for it.
It's a minor but important point. Lets not kid ourselves here.
I don't think anyone is under the illusion that education is free. However, it benefits society as a whole, and not everyone may be able to afford it. So, it is often in the interest of society to make good tuition affordable, regardless the background of a student.
Of course, it is also beneficial for the student. But for that we have the tax man :).