Do you have a citation for your tobacco statistics? Not trying to be an ass; I've just heard the opposite is true for tobacco. Something like 70% of people who begin using it casually eventually become addicted.
I can't find anything right now because it's not a very common statistic; most of the research focuses on how hard it is for people already addicted to quit. I definitely did read that stat somewhere though, although I think the exact number is somewhat controversial. If you dig around enough I'm sure you can find the research though.