It's my impression that fewer performers drink alcohol on stage than used to in the past: part of this may be "health and safety", screwtop water bottles being safer among all those electrical cables than potentially spillable glasses. Also maybe looks better to not be seen to be drinking alcohol on stage, though that does not exclude it happening backstage either before or after!
What surprised me is what some agents build into their performers' contracts in the way of "riders". OK, they might need some sort of meal and tea/coffee/water/juice if they've come a long way, but "3 bottles of best Rioja" (sic) between 5 performers? They are getting a good fee: surely if they want alcohol they could/should buy it themselves?