There is no universe where a multi billion dollar bank is going to let billions of dollars of loans evaporate. They have all the connections in government and the all the right people out to dinner to prevent that.
Instead, the banks will get their bad loans paid off by the taxpayer. This further incentivizes them to embark on worthless loans as they know there can feel a nearly infinite stream of money into their pockets.
The best solution is education: nobody should take out a 70k loan for a job that could only pay 30k. The second is default: lenders should feel the sting of making bad loans and_should not_ be rewarded for bad behavior and taking advantage of kids.