I don't smoke cigarettes, but I do smoke a cigar maybe 4 or 5 times a year or so. Addiction is an obvious thing to keep it going, but how it starts is interesting. Here is my view.
1) It's a drug. It does have an effect beyond addiction, though minor. It's a stimulant, and can calm people down. Caffine is stronger of an effect and less dangerous, but still, its a factor.
2) I'm not so sure about Cigarettes, but Cigars can smell absolutely amazing. I like that I have friends who smoke, because even a cheapo Black and Mild smells great.
3) Why do we shake hands? Wave? Or a million of other little social contracts? They are, in many ways, the equivalent of small talk, a simple, communal activity that bonds everyone involved. A bunch of people talking are just talking, but if they are all smoking, then that is a social group. Think about it. In a war movie, filled with big, tough, men's men, if the director wants to show a moment of camaraderie amongst the soldiers, what does he do? They share Cigarettes, a simple act like giving someone a light is a stand in for being willing to do whatever it takes to save your new brother.
4) It looks bad-ass, or at least more dynamic, then someone with their hands at their sides. The lighting, clenching between teeth, the trail of smoke, the exhale, all adds a little action to liven the scene up. Also, a willingness to smoke while doing something serious (Like, say, fight or shoot) implies that the action you are taking is easy enough to also concentrate on your cigarette at the same time. In addition, we now all know that cigarettes can kill you: Though that decreased smoking overall, it also means that a smoker is showing a reckless disregard for his own health and safety, which, lets face it, is a common type of badass. It also come across as, "Not Politically Correct", which is another thing that people will just eat right up.
All that is enough to get the person hooked.
