The reality of it is that Steve is right, alcohol inhibits us, so most folks cannot function as well after drinking as they would otherwise. No argument.
The "other" reality is a matter of how much drinking affects us, versus how it affects other parts of our world. Meaning stress, anxiety, tension, nervousness... Sometimes the real world comes crashing in and we're not at our mental best when we arrive at the pool room. A bad day at work, problems at home, any numbers of other factors. Should we be able to put those concerns aside, and play to the best of ability, yup. Can those issues affect us and our ability to concentrate, and/or relax, yup.
Drinking to mask those (or any other) issues isn't necessarily the best answer. But in the real world, a small amount of alcohol might just take the edge off your day, and let you play the way you might otherwise. In moderation.
And one more time, Steve is right. Alcohol will inhibit anyone, depending on their tolerance and how much they imbibe. The question is, how much is too much?
I play to enjoy myself. If I'm all tense and wound up, I am not going to shoot my best. I will have a small drink to loosen up, and let me think about pool, not the problems of the day. Many nights I won't drink until I'm done playing, because I'm feeling fine and am having a fine old time as it is. Depends on the night. I don't come strolling in, getting a drink before anything else...and I don't want it to be a crutch, meaning that I "have to have a drink in order to play."
This is league play I'm talking about, or our small in-house tournaments.
I'm pretty sure were I to ever play in any sort of "big" tournament, I'd be keeping the consumption to a minimum, if any at all. Hopefully I'd have the rest of my world in it's proper place going into it that day.