Drunk tripping can be a bit crazy/dangerous. The inhibition reduction of the alcohol & the strange thought processes things like LSD cause can result in people doing kind of ridiculous things... Sometimes that can be fun, sometimes not so much. These are the types of things that result in people ending up naked in the reflective pool at the washington monument or throwing whiskey bottles at mailboxes in gated communities. Now while there's nothing inherently wrong with either of these things, they can have unpleasant consequences...
This being said, i drink when i trip fairly often. Not all that heavily though. Usually I dose an hour or two before I start drinking, depending on what I'm taking. Then I just casually sip beers over the duration of the trip, that way when i'm nearing the end of the psychedelic effects, i'm also getting relaxed & sleepy from the beer, Definitely eases the comedown phase, sans benzos. Also, i'm a bit of a beer aficionado, so having a few good beers during a trip is a rather pleasurable experience for me.