On a more personal note, I smoked pipe tobacco for a while my first year of college. My reasoning was I wanted to join my friends when they went out for a cigarette since a lot of them smoked cigarettes, the pipe tobacco smelled good, and I liked to play with the smoke and watch how the air currents acted and whatever because I'm an aerodynamics nerd. I can confirm that I didn't get addicted because I just stopped doing it one day and never gave it a second thought. I'll still smoke hookah or a cigar if the opportunity arises, but I never go out of my way to smoke something. Especially cigarettes since they smell horrible.
Whether or not I care what other people do to their bodies is not only irrelevant, but should not even be a legitimate question.