College loans are not dischargeable in bankruptcy. Simple as that.
With lenders knowing that the government will make sure they get paid, they’re happy to loan out any amount of money to anyone regardless of credit worthiness, because they take on literally zero risk.
Then colleges realize the same, and jack up their prices in turn. The feedback loop brings us to where we are today. There is no market (or other) force putting any downward pressure on tuition costs, at all. This is the inevitable result.