Binge drinking has become a very harmful and dangerous activity on college campuses. You see it at parties, or other similar social events on a college campus. Placing restrictions on alcohol consumption could possibly save lives and other harmful injuries. On the other hand, students may ignore the restrictions anyways.
Already many college age kids drink under 21 binge drink. What would change by putting a restriction on the act in general, age or otherwise? One of those important parts of the college age is learning your limits. It's good to know exactly how much alcohol you can drink before getting sick, or blacking out. You wouldn't want to show up to work hung over, after college, because you had a few to many.