It's all seen as part of recreation. If you don't get drunk, you didn't experience recreation. We have had the same behavior for years with other drugs. I think most students binge drink because they don't know how to drink otherwise. This sounds strange, but think of when they started to drink and what the reasons were for drinking.
Many students learn to binge drink before they become social drinkers.
Another idea of binge drinking is that it is a reflection of American drinking practices in general. For decades Americans drank heavily on the weekend and then went to work. Drinking on the job has been looked down upon. I think the practice is a carryover in many ways to college practices that students can't wait for the weekend to get wasted. Which students become alcoholic is often difficult to determine.