"They aren't required to, but if they make a good deal of money and refuse to help their kid out with college in any way it can drastically affect their ability to get financial aid."
This issue works in both directions, though. In the OP's situation, his son was hurting his chances in the interview by refusing to take clothing advice. If that refusal resulted in a situation where the kid needed to borrow more and had a hard time because mom and dad have a lot of money, then frankly that's his fault and I see it as a good lesson to learn.
"The problem with the university issue is that the consequences can vastly outweigh the behavior. Blowing a scholarship interview can lead to less money for university. The parents then saying "Sorry, if you don't care enough to try, we're not chipping in the extra" does sound like a logical consequence. But the ability to get student loans is generally linked to parental income. So if the parents make a good income, but aren't paying for university, it can push the teen from being able to attend university, to not being able to, and that has long term repercussions for career and financial security."
See above. There are a number of mistakes that one can make that have long consequences, and on the scale of such things having to skip going to college for a year or two or five still falls pretty far down the list. Sure, it'll have a significant impact on the teen, but finding out that s/he's not going to be able to afford college in the fall is a lesson that won't be forgotten the next time the interviews come around. I just don't see having to work for a year before college as such a horrifying consequence that it's to be avoided even at the expense of not letting a nascent adult learn to deal with real life.