I don't, and there are a couple reasons why I don't; for one, it's terrible for your health, and my eating habits aren't exactly the healthiest, so why would I make things worse by inhaling chemicals? That brings me to my second point - what is the point of smoking cigarettes? I can understand why people smoke pot because of the feeling it produces (provided you've got some good pot) - cigarettes, on the other hand, don't really produce any feeling whatsoever. The first time you try them usually results in a coughing jag, and the only benefit people seem to sight is that it "relaxes them" or "mellows them out" - funny, I can think of a number of activities that do that very thing, and all of them have a far less likely chance of killing you
Furthermore, cigarettes are really expensive - so, 1)unhealthy, 2)no significant "high", 3)expensive. Taking all that into account, the only logical conclusion I can come to is that smoking is a fucking retarded habit. I also laugh to myself when I see people at my work who smoke at least 3 times within a 6 hour period and go on about how they aren't "addicted" - bullshit.