Typically, a loan with interest is a gamble. You want to get your money back with a return. If you loan money you want to ensure you will get your money back by qualifying the applicant. There is a risk though because they might not pay it back, thus you increase the interest rate according to how qualified the loan is. Good investors really focus on getting a qualified applicant (one that can pay it back). Sometimes they don't get their money back and they are forced to write it off - it is apart of the loan business.
Basically, I am not trying to be insulting but I will end up explaining how a loan works - so I will stop there.
With college loans ALL basic loan concepts are wrong. You cannot default on a college loan by law. It follows you through marriage, bankruptcy, or even service in Afghanistan. The people which made these poor loans know they made poor loans backed by the US government. Thus, they have lobbyists pushing congress to ensure student loans are 'unforgivable'. SO! Investing in a student loan is a damn good deal. You have 0 chance of someone defaulting because it is illegal to default. The loan has zero risk. This is why tuition has exploded and why we have a crisis.
So, if you want to major in 18th century French Dance at Yale for 190k - there isn't an investor willing to stop you.