Perhaps because we now see childhood as extending much further, and college as more an extension of highschool? I mean, you stay on your parents health insurance until 26, and most students are having the bills largely paid by parents. According to this report, its 41% parents/relatives (savings+loans), 34% scholarships, 25% students (income/loans). So 75% of the tuition is the University and the Parents, and that's not even counting all the other sundry expenses.

http://news.salliemae.com/files/doc_library/file/HowAmericaP...

That and we now are emphasizing college as a must-have entry to getting a legitimate career, so we have to make it prettier and more mainstream since huge masses of people are willing to spend large amounts of money. Decades ago, it was for the few who wanted to pursue higher education out of genuine pursuit of knowledge, and was much less expensive.