Well the reason I mentioned religion is because in Islam drinking alcohol is considered a major sin (the mother of all sins, actually) and is grouped with gambling and sex outside of marriage (which unfortunately are also BIG parts of American culture). I do know a select few Muslims who still drink anyway but they aren't really 'practicing'. It's just that I consider myself a very religious person and I have a tough time finding people who have that same sort of mindset.
One other thing my mother's family (which is Christian) has a bad history of alcoholism as well which has also helped me stay away from it.