I don't deny it. There are considerations in both directions. You could also imagine a system of universal rate setting, where you can only offer loans to potential engineers if you do so to art students as well. You could imagine genuinely allowing a free market in student loans. There are a lot of possibilities, each of which would fall at different places on the multi-dimensional optimization problem that we've got in front of us.
But I argue that if you want folks to offer student loans, and don't want lenders to discriminate against certain majors, and don't want interest rates >10%, and want principles on the order of >$100k, you probably need to prevent discharging the loan in bankruptcy. You can't get all those other things and dischargeable loans at the same time.
Well, maybe it would have been better this way.
This way universities would be forced to be affordable, and use the money for teaching instead of today's tuition costs that goes 50% for a new stadium, 45% "administrative costs" 5% teachers and TAs