Spherical cows. You are applying economic theory in a vacuum. Sure, we joked at the time we could just declare bankruptcy and keep the degree. However, show me sources showing that this was a real problem. It wasn't.
Simply, people were not playing the game that way in any serious way. I am pretty sure I have never met a single person who declared bankruptcy purely to avoid a student loan.
People might not do it for a $15k loan (accounting for inflation back then), but they definitely will for $100k today. School was much cheaper back then.
Simply, people were not playing the game that way in any serious way. I am pretty sure I have never met a single person who declared bankruptcy purely to avoid a student loan.