1. Boredom. Smoking is something to do. In many places, they offer smoke breaks to people who smoke. So instead of sitting in your cubicle and hating your life, it's very refreshing to take a five-minute break. Of course, you don't have to smoke, but a lot of people do because of the next point.
2. Community. There's pretty much always a designated smoking area, and the people who go to the smoke pit usually become friends. It's some social interaction for a little while during the grind of the day. And if you want to be a member of the little club they've got going, you have to smoke.
3. Stress relief. This goes along with the social interaction, but the nicotine itself definitely calms people down.
4. Keeping awake. I've done this myself - I usually sleep from 2000 to 0400 (8 to 4). And suddenly on the weekend I get stuck on guard duty from 0000 to 0500. I'm tired as hell and trying not to nod off. So I bum a cigarette off someone and smoke it, and I'm good for the shift.
5. Peer pressure. Let's say you're a non-smoker, but all of your coworkers are. They go on smoke break, and you're the only one who's in the office. What are you going to do, twiddle your thumbs until they come back? No, you go out into the smoke pit and hang out until they're done. Sooner or later, you start joining in, smoking a cigarette here or there, and it becomes a habit.
