What is broken with student loans is that the current scheme messes with almost every sensible market incentive out there: Colleges get more expensive for little to no reason, people can get into big loans for degrees that will never pay off, and the companies lending the money are, in practice, guaranteed repayment by the treasury, so ultimately the whole scheme leads to far higher prices than, say, college in Europe, but only provides better outcomes for some school+major combinations.
Let's not forget, the system leads to degrees that have low expected values to end up being unaffordable, while prices would go down if the system wasn't built with the silly guarantees that it has. Putting the blame on the borrower alone and ignoring the insane system design is just shortsighted.
If someone went to try to launch pets.com today, we'd not blame the founders alone for the VC's loss: They carry responsibility too for betting on a horse that had no chance of even finishing the race. A VC takes risks, but also expects losses. Anyone making loans should consider chances of delayed payments and of losing all the money completely.
Let's go back to your idea of protocols. Imagine we are making a requests over a network and expecting the network to not be lossy, and to never have long network partitions, or for other servers to go down. We can be angry at the network or the server on the other side, but in practice, what we do is understand that failures exist. Expecting everyone to pay you back all the time is like expecting a distributed database to be reliable all the time. I can scream at the network or the database vendor, but ultimately the joke is on me for expecting impossible things.