Personally, I do. I also realize that I may be in the minority here, because i rarely drink at all. I have cliets (big $$ people) that demand that the musicians do not eat or drink at their functions. We're hired help, not guests.
If you ever work country club circuits in high brow neigborhoods and reach for a snack in a buffett line, you'll find out just what I mean. We're not hired to be part of the party. We're more of a front runner that paces the party. We need that "sparation" from the crowd, while at the same time act as ambassator to bring the room "together". It's not easy, and it's harder when you are not playing your "A" game.

Drinking (wisely, or not) takes your game down a notch. I can't afford that.

As for "needing to relax" - that's a load of crap. You function during the day at work without the drugs, why is it different at night? Work is work, and drinking on the job is just foolish. At least that's how I see it.
I realize that without these "sin products" like booze and tobacco, the music business would be severely affected, but I'm all for the smokeless, daytime venues that have none of the perils of yesterday as a main rule of thumb. Drink if you want to, but please don't try to convince me (or ANYONE)that you play BETTER because of it. You'd be lying to us all. Confidence doesn't come in a bottle or wrapped in paper.