(1) rwc38 is right. Tailgating is never happening at BYU because everyone is already down a day during the week. Most fans have to get some things done on Saturday that the rest of the country can do on Sunday.
(2) It is a LOT easier to get loud and rowdy with the help of alcohol. Even if you're not drinking it is a lot easier to get loud and rowdy when the guy next to you IS drinking and already getting loud and rowdy.
With that being said, I agree that there are a lot of fans in the stands just to support the church. I swear I am surrounded by them every game as they talk about everything but the game. I don't know what can be done to change this, but I do think it detracts from the atmosphere. Maybe I'll do my part this week and tell the lady sitting behind me to shut up, stop gossiping, and watch the game