Agreed. But it seems easier for bochurim to quit. I'd venture a guess that many bochurim who were addicted and "quit" easily, when they wanted, even for a few years, end up taking up smoking or another addiction at some point later in life.
Thats just my anecdotal observation.
From my limited understanding and reading, it would seem that the psychological addiction is not as strong, because the user never intended to be doing it long term. Someone who cannot imagine life without cigarettes is going to have a harder time stopping than one who doesn't envision himself going through life with cigarettes. The psychological dependency seems to be less when one always planned on quitting before a predefined period. Most boys know that they're going to have to stop before getting married, and never plan or dream otherwise. This doesn't make stopping easy, but I think the dependency developes to a lesser degree. I am by no means an expert.