Largely because there is another debt bubble keeping it afloat, the student debt bubble, which has driven up tuitions and enriched college towns. Our local economy is particularly vulnerable to mass defaults as students are overwhelmed by their debt loads and as the ethics of lenders become more and more suspect. See http://www.counterpunch.org/2012/10/26/american-students-the-coal-miners-of-today/ on "Student Debt as the Choke Point of Financial Capitalism."
College towns also have the advantage of a small-town experience and the value of this in raising children (less crime and stress and an environment more nurturing to a child); often the connection with Nature, local food, and hiking/biking; the remarkable cultural stimulation, comparable to a large city in some ways; the youthfulness and energy and progressive politics of such towns. All these factors play into it.
But the fundamental of more stable employment and the "wealth" created by the student debt bubble is the overriding cause here. The exploitation of college students by credit card companies is yet another facet of the student debt bubble.