> The mechanism by which you default on a loan is bankruptcy. If you can't discharge a loan in bankruptcy, you can't default on it.
This is absolutely, completely, 100% wrong. Defaulting on a loan means that the borrower has failed to repay according to the agreed-upon terms.
> Some people never make enough money to pay it off, after which the government will pay the loan off after a few years. The lender gets payed anyway.
This isn't really true either. The lender is not guaranteed to be paid their principal back.
> These are risk free loans for lenders.
If these were truly risk-free, then the interest rate on private student loans would be roughly equal to the current actual risk-free rate of investment (because any new lender could always capture additional loans by undercutting their competitors and still make a profit).
Except, that's not true at all. The interest rate on private loans is quite high. In fact, it's significantly higher than the interest rate on mortgages, which are loans backed by collateral that can actually be seized.