Complains about having to go outside to smoke, and compares this legally mandated, cancer-preventing courtesy unironically to segregation. Tries to rally other smokers to his cause, though they never respond with "we have rights, dammit!" Goes through entire routine for every publicly consumed cigarette.
Has a big report or project due later that day, and is completely fried. Convinced that spending the time it takes to smoke a cigarette is an investment in working smarter and not harder. Only smokes when stressed and would not call himself a smoker. Smokes five times a week.
Smokes because their friend is smoking. Even though they're an adult, thinks they're getting away with something. Calls cigarettes ciggies, and does so often.
Only smokes when drunk. Has no memories of smoking. Smokes an average of a half-pack a day, so is probably an alcoholic but not, technically, a smoker.
Smokes because it looks cool, especially with his haircut. His silence is mistaken for coolness, sometimes depth. Is probably in the Strokes, because the Strokes are really cool.
Members of "The Greatest Generation" are not quitters. They finish what they start. Back when they were young, everybody smoked, and you weren't a man if you didn't have a pack of Luckys with you. At least that's what it sounded like when he said something through his electronic stoma voice box thingy.