I'm not an expert on human psychology by a long shot. But I do know that a significant percentage of teenagers feel the need to attack their brains with drugs and alcohol on a regular basis. My friends and I felt that need back then. Kids of today still feel that need. There will always be a core group of substance abusers on any campus whose influence on student culture will wax and wane for reasons that have only little to do with university policies toward alcohol and drugs.
Substance abuse is embedded in the fabric of college life.
We can win small battles on our campuses in fighting alcohol and drug use. We should fight those battles, but we cannot expect to win the war. For many, it's a right of passage. In your teenage years, emotions are at a peak. And maybe because of that alcohol and drugs are so attractive.