Alcool, drugs, cigaretts are honestly things I do not understand. I know I'm still very young (19), but I never had any interest toward them and I never plan to take any of them. For once, the effect it gives is basically getting people less rationnal so the conversations you have are less interesting, it attacks your liver, it makes your breath stink, it gives you a headach the day after, it's relatively expensive, for cigaretts it negatively affects your cardio, etc. Yet, most people do take them I don't what is it social pressure? Some kind of need for conformity? Some kind of need to get out of your normal state of mind? I don't know, but since it's a real issue I guess it should be dealt with and rationality is not the way to go because addiction is beyond rationality. I still find it idiotic that what most people of my age drink when they get together is alcool instead of water or juice, I don't know is it's for the taste itself (I doubt it) I think it's for the effect or just to conform, it's sad...
Well, first of all, I think there are many drinks that contain alcohol and taste very well. I live in Belgium and I can tell you that certain beers here are absolutely delicious! They offer a richly tasteful experience. The same goes with fine wines and good whiskeys.
On the other hand, there's no denying that heavy drinkers consume alcoholic booze for different reasons. They want to escape from reality for a while. Sometimes it doesn't go much further than simply relaxing for a bit and enjoying a couple of pints or a few glasses of wine, while carelessly having a chat with your friends. There are other times, though, that you want more, you want to be even looser, you want to go on an adventure that you wouldn't go on if you were sober. You start exceeding boundaries. There are suddenly a lot more realistic opportunities to make life more interesting.
You seem to have a very rational point of view on things and I partly am a pretty rational-minded person as well, but on the other hand I also like variety. I can enjoy watching a great film, having an interesting discussion with someone or playing a good game of tennis, but also being drunk as a monkey with some friends while doing some 'out of the box' crazy stuff. There's a time and place for everything, in my opinion.
Of course there are dangers and serious drawbacks to alcohol and drugs. You don't have to tell me that as I've been confronted with many of them. It's just a matter of finding a good balance.
There are people (like you seem to be for instance) that genuinely don't care about "leaving their usual state of mind" and their own capacity to think rationally and who are perfectly happy to live life without ever going out of that comfort zone of self-control. That's perfectly valid and perhaps even the wisest thing to do in the end (taking into account all the factors), but I'm also convinced there are people who can function very well and live a happy life even though they drink large amounts of alcohol at times. A good example is Christopher Hitchens for instance (who is an intellectual I respect very much). His productivity is legendary and yet he was an extremely heavy drinker. The reason he gave for drinking so much alcohol, was that people profoundly bored him when he was sober.
As for smoking cigarettes, that's a whole different and more complex story. It's incredibly bad for you and noone should ever start smoking, but as a smoker, smoking a cigarette is somehow still meaningful to me in a positive way. There are few things better than smoking a cigarette in the middle of the night, looking at a starry sky and thinking about existence for a moment. Smoking casually is probably more like a habit that has become an addictive desire, but I still enjoy it in a weird way. I'm sure I'll quit smoking when I'm a bit older because of health reasons, but for now it's still a part of me that I don't want to leave behind just yet. I'll also admit that I love the old-fashioned aura of it (when done in the right situation). Sometimes I think of myself as a really stupid person who's overly sensitive to nostalgia...