I assume the rationale is that it's the student's fault if he chooses a major (e.g., sociology) that doesn't cover interest afterwards.

Well, if you say so? Of course, it grossly oversimplifies reality. Job markets are complex; lack of success cannot always be traced back to bad choices. Also, you could level a very similar objection against health insurance. Personally, I'm not comfortable with that kind of senseless cut-throat capitalism.