If the school is making a commitment to give them a free education, while allowing them to earn some money, then I do believe the student athlete should make a commitment to the program and himself(most importantly) and earn a degree.
If they just decide college isn't for them, then I hope they have a better option financially than what they're leaving. If dangling a trust account in a kid's face makes him stick around and earn a degree(for free by the way), to better his life, then so be it.
Now I know, college isn't for everyone...blah blah blah. If you don't have any other great options at the time to go make your own startup internet company or some other nice deal, then why not just stick it out and get the degree and open up other doors in your future, simply by having it.
In special cases, like medical, or family emergency(not a crazy mom!...wink wink), that could be something arranged between the school and the player...keep the NCAA's greasy fingers out!!!!!