We tried one session that let people drink - mostly it was an unwritten rule especially since we didn't have any on hand.
It was a relaxed evening, two people had their birthdays that same day - so it was more of a get together. We all got about 1 hour of game in, partly because we then got distracted with other stuff. I don't primarily, but partially relate this to alcohol. We frankly weren't interested in the game and the DM(new to dm-ing), and we didn't appreciate some of the ways he was trying to do things (though different from usual). Not into it.
I don't have a problem with people drinking at my table... drunk is another thing altogether.