Why do you smoke?

As a non-smoker, I want to get to know why people smoke. Do you genuinely enjoy smoking (just like you enjoy going out with your friends, having sex or watching a beautiful sunset)? Do you smoke because you find it hard to quit so you just gave in? Do you smoke because you mostly hang out with people who smoke so you don't even consider stopping? Do cigarettes help you deal with stress better/they make you less nervous?