I find your story interesting because I had a similar experience growing up. While there have always been drugs in the schools I went to (and my friends were often the ones who used them) I never really got into them. I'd tried pot and alcohol, and I wasn't really impressed. Pot didn't do anything for me and alcohol didn't really taste very good. I'm a stickler about drinking stuff that tastes good, so I put it out of my mind.
However, over the first few years of college my friends did fewer drugs and drank more. Not all of them drink, but enough do that it's part of our little group. I thought of it like you do - that they were betraying this psudo-clean living vibe we had going. We used to be too good for this crap. However, I figured I couldn't judge them without getting drunk and seeing how it was.
So, at our new years party, I found a drink that I didn't hate (lemonade of some alcholoc sort) and drank that. I guss I got drunk, though I don't have much of a scale to measure it on. I ran around, did some minorly stupid stuff, laughed at dumb jokes, etc. I had a really good time. For a while, I was humbled. I had seen drinking as a stupid, even reprehensable, thing to do, but I enjoyed it as much as anyone else.
Now I'm not so sure about the evils of alcohol. It's true that I lost control of myself, and all the drawbacks of alcohol you list are also true. I can't help thinking that it was fun and that I might enjoy it in spite of all the drawbacks.