Wtf is up with Californian drinking prohibitionism?

Just recently visited some friends in L.A. (I am from the UK) and was shocked at how taboo drinking alcohol is. These people will literally go to AA if they happen to have more than 4 drinks in one night. Not saying the UK doesn't have a drinking problem, but how has this puritanical mindset taken over? My friend's brother is claiming to be a recovering alcoholic at the age of 21. It seems like this longevity and optimisation culture has started to infect everything there