"I'm a Computer Science senior right now, and sure, I could have learned all the stuff I learned from buying my own books, but I never would have."

One of the weird things about college or university is that it gives one social license to spend four years, or more, learning something as an adult.

If you were not enrolled in a university, but instead diligently reading books, solving problems, writing essays etc. for four years without being otherwise employed, people would find you eccentric at the very least. But once officially enrolled at an educational institution, society thinks it is not only perfectly fine to do the same things, but to take on large amounts of debt for the privilege of doing so.