However, there is social pressure. The social pressure that makes that given your social level and how smart you are, you are much more akin to fall into drugs (tobacco, alcohol) if it's allowed.
Take it this way: It's incredibly hard, today, in France, to explain someone smoking at a bar outdoors that he's reducing your life expectancy. It's incredibly hard to find bars to go to. It's incredibly hard in my city (Lyon), to walk on the sidewalk and avoid smokers. It's impossible to run around our park without being under the smoke of smokers - and that's the only place where asthmatists can go running.
Smokers don't even think of smoking as harmful in practice, even if they admit it in theory.
While I'm unhappy with the war on drugs and the class domination it represents (jailing the poorer and the political opponents), I'm incredibly happy that I don't have to explain my friends that they can't come to work with drugs or that we don't have to explain children that drugs are legal but shouldn't be bought. The law makes things clear: It's forbidden because it's bad.
And I'm happy that I'm not proposed drugs during cocktails, while I'm insistently proposed cigarettes and alcohol.