Because that was the deal.
When discovered to be so, it's also possible to alter the deal.
Regardless of whether that kid should have been free-thinking enough to see outside their existence's bubble, it's irresponsible to exploit their ignorance for profit. Most of these kids haven't ever seen a debt-ridden life like they're signing up for. I grew up with parents who ranted and raged about debt, and I still did it. Are you sure the problem lies with the kids signing the papers (I guess clicking the "Get your loan here!" button these days)?