@Draugnar: well, I genuinely understand the confusion this time, but I was bringing it back to the OP a bit I suppose. And I mean, what makes you think I care about American cigarette-laws? :)
As for your question: for the same reason illegal guns don't really work on any reasonably sized scale over here either. For the same reason our "war on drugs" is going fine.
Because we have better control apparently, or less organized crime, or both. Unlike in the USA perhaps, it would actually be a big hassle to get the cigarettes, and you'd be damn sure not to smoke in 'borderline' public, so you don't have to go through cigarette-smoke when you get out of school.
Really, I know many people who smoke and I'm fairly certain many of them would stop if they couldn't get it easily, nor legally.
I don't care too much though, but I would support banning cigarettes I think.