The incentive structures are completely screwed up. The government has no incentive to halt or slow down these loans because they persist even through bankruptcy. Universities have no incentive to lower costs because the government will provide their customers -- err, students -- with the money to pay for it. And students aren't incentivized to forego school because a college degree (hell, even a graduate degree) are baseline requirements for gainful employment.
What's interesting to me is the mental exercise that comes about viewing this as a challenge to overcome. What's the alternative to this system? I can only think of individual actions, not system-wide solutions.
edit to add: I can imagine a political solution that involves the government buying debt, but Bernie's revolution stalled, so I mean something else by "system-wide solutions".