The last two times I was in F on AS I heard an FA ask a passenger "You aren't going to be driving, are you?" before refilling their glasses. It surprised me to hear it two flights in a row from different FAs. Maybe they are instructed to ask this?

As a non-drinker it seems like it would be easy to just have a 2 drink limit or something (as long as they give me all the Diet Coke I want, natch.) But it's obvious some folks would find this unacceptable. I don't envy the FAs in this regard.