You are wrong. Interns are paid 75% of starting salary and don't work more than a few months. Many of these people are a year away from entering the labor force. With housing costs it's hard to take home more than a few k.
It actually doesn't. New grads at Google were getting ~$85k in 2006. By the CPI, that's ~$101k now. If "graddie" salaries were any less than that, wages would have actually decreased.