A lot of kids probably drink "thinking they won't get caught" or thinking administrators/coaches/parents "will just let it slide" because too many people do just let it slide. If every kid who got busted had the hammer dropped on them -- whether state championship contender or JV freshman -- then it'd make some kids think twice. Not all. But some.
I went to a high school where athletes in the school's biggest sport had slaps on the wrist for first and second offenses while other sports cracked the whip on their kids. Most of the time the kids in the spotlight sport drank and took their chances because they knew their punishment for getting caught was sitting out a half or not getting to start for a game or two.
And I agree, why have contracts if they are not upheld? What message does that send? For a quick example of this, look at who started on the offensive line for the Colts in the Super Bowl last night. Former SM Northwest player Ryan Lilja. Remember the uproar back when he was a senior in high school? He got busted for drinking a beer at a party. He'd signed a contract, as had his parents, so he was done for the season. His parents tried to sue to get him back on the team, but the court said "you signed a contract." Lilja lost his DI scholarship, played JUCO ball for two years, went to K-State and still made it to the NFL.
Punishing the kid doesn't ruin his life unless the kid lets it. And if that happens, that's the kid's own darn fault.