Oh... it's not a very long story, actually. I was at a picnic one day with my father when I was young (probably around 6 or 7). I asked him if I could have a sip of his beer, and being the "cool" dad that he was, he told me I could have a whole beer by myself.
He had one condition, though -- if I opened the beer, I had to drink the whole thing. Of course I agreed, and with a big smile on my face, I opened up my first beer. I couldn't wait to tell my friends how cool my dad was.
One taste is all it took -- I hated it. My dad stuck to his guns, though, and made me drink the whole thing. By the time I was done, I had thrown up twice, and was sick for the rest of the day. I don't remember feeling drunk, but I'm sure as a 6 year old, I was, and just remember it as feeling dizzy and sick.
Of course, beer doesn't make me sick any more, but to this day I can not stand the taste of beer. Some say it's an acquired taste, and I have tried, but I just don't like it.
Incidentally, he once made me eat all the tobacco out of a cigarette when he saw me pretending to smoke one. Guess what? I don't smoke, either.
So... that's why I don't drink beer. You may think "wow, what a cool lesson," but I really think he went a little over the top.