The premise at least is that if you hold kids responsible for their own educations, they'll choose careers and topics of study that lend to paying off that debt. If you let kids mess around in college for 4 years with no financial incentive, they might all study underwater basketweaving.
I don't buy that line of thinking at all, but some surely do.
So it looks like the cost of college is yet another burden the boomers have placed on our doorstep (and even more, the doorstep of those younger than me). I'm skeptical that saddling 18-year-olds with mounds of irrevocable debt has any merits to speak of, but am curious what argument could be made in that direction.