I partially agree with you. I never understood why people smoke, but when it comes to drinking I do it on occasion. For me, I'm not insecure, depressed, anything like that. I never drink by myself. Drinking is moreso a social thing for me. I love the atmosphere of a bar or a cocnert(espically here in Austin), being around great music and a ton of people -- most of which are drinking themselves. Usually I stick to just beer. I'll admit I acquired the taste and it's kind of fun to try different and new beers. The effect of alcohol on me is that it makes me more social. Being a generally shy guy when I first get to know someone, I find that I can much more easily talk to anyone after a few beers. I'm not saying however, that I can't without. Nor am I saying that it makes the night more or less fun. It's just something to do. It's when people overdo it, do it for the wrong reasons, or make an ass out of themselves when I see it becoming an issue.
Regarding smoking, I've never smoked a cigarette in my life. It's never appealed to me and doesn't do anything for me. I often try to analyze why some of my friends smoke -- I think it's mostly due to insecurity, but also because of the social aspect. However, inhaling smoke into your lungs seems FAR more dangerous to me than having a little alcohol in a beer. Pot smoking I see as less bad, and it does give you more of an effect, but I'm usually just happy sticking to beer for an effect. Plus it's easy to learn your limits with beer.
Anyway, in summary, I don't think that drinking is so bad as long as it's not overdone. It's merely a social thing, much like any other harmless thing you would do in a social situation where it is present.