Actually, I learned recently that it is from rosacea, yet another fun condition. When I went to a dermatologist, he talked about my hair, but then he mentioned that I have red cheeks, and suggested that I have rosacea. So he prescribed Azelix (sp?) for me, which he said I should apply to my cheeks 2x per day, for the rest of my life, or until they find a cure. There is even a makeup you can buy, because (and this is true in my case) you look stupid giving some corporate presentation when your freegin cheeks are red. Looks like you are embarrassed when you aren't at all.
Other triggers for redness might be vinegar, sun, working out, etc. I think my cheeks might get a little red just after applying minoxidil, too.
Rosacea is commonly mistaken for alcoholism, for the reason that you said. You should try to treat it, since it can get progressively worse, and spread to your nose and beneath your eyes. Bill Clinton has rosacea, and look at his symptoms.
Good question though. Aren't you glad you asked? =) Go see a dermatologist about it. There are also oral pills to take. Look it up on the web, too. These things are just being discovered, because people like us ask "why do we have this condition, and others don't". We are learning a lot in this day and age.