We’re so obsessed with stopping cheaters or lazy good-for-nothing’s that we’ll privatize at all costs. That’s including, oddly enough, publicly distributing the risk those private institutions take on. Why not just cut out the middle man and have the government pay for the higher education of the low and middle class directly?
The purpose of loans is that the private sector should be able to better evaluate college ROI than a government agency and offers/prices appropriately. Admittedly, government loan backing breaks this model.
(Also it doesn't help that the least risky students are out of the pool by either parents funding or scholarships)