Unlike the other divisions in NCAA competition, Division 3 schools like Washington University and the University of Chicago, two schools with excellent economics programs, do not offer athletic scholarships. Because of this, the NCAA can't threaten the loss of scholarships in D3 when programs go rogue (no Sarah Palin pun intended). Moreover, like most players in all divisions, most D3 players have no chance to play professionally.
Despite these facts, athletes still they still have incentives to spend a lot of their time on their sports at the expense of their classes. Now some D3 schools are concerned that athletics, to too much of an extent, are trumping academics:
They play for the love of the game, not with the hope of landing a pro contract. Without athletic scholarships, many even pay their own way to school.
The notion of student-athletes as students first is integral to Division III, the NCAA's largest classification. But a growing body of research shows a considerable gap in classroom performance between Division III athletes and their counterparts in the overall student body.
What's a little ironic is that the University of Chicago famously dropped its football program back in the 1930's because of fears that athletics would trump academics. But even at the D3 level, student-athletes, coaches, and administrators feel the pressure to win. Just because the spotlight is dimmer in D3 doesn't mean those incentives aren't very real.
Update: TSE comments are usually thoughtful and enlightening, but IMHO there are especially great comments to this post. Dennis Coates makes a great point about the athlete's behavior being utility-maximizing. Since there are no athletic scholarships and the D3 students attend school on their own dime, why should schools be so vigilant about how they spend their time? If I attend a D3 school and I particularly like the History of Western Civ, is it bad for the college if I spend more time studying my Western Civ at the expense of, say, Money and Banking when I'm footing my own bill? Similarly, if I particularly like playing football, is it bad for the college if I spend more time studying my playbook than I do studying my Chemistry?
Update 2: It's been argued that a well-rounded education is one of mind as well as body. Taken at face value, if a student decides that his/her best use of time is to focus on fitness of body at the expense of "fitness of mind", is this a bad thing in all cases?