One of the root causes of the "college bubble" might just be completely overlooking this question, or taking any number of half-hearted answers for granted... or thinking that the relativistic mindset which has beset academia in the last 50 years is the final frontier.
Currently reading "The Closing of the American Mind" (as an American, wearily) and finding the history of the university as laid out there very interesting.
(Trying to formulate a general opinion but the deeper I go, the harder it is.)
There are countless difficult questions and choices which face man, and in most institutions of higher learning, they've taken a backseat to questions of employability & cost.
On an unrelated note, the new undergraduate business school building at my alma mater cost $55 million.