I think the main reason for smoking is the advertisements which encourage people to smoke. Some people say that they enjoy smoking and it is fun to do so. Some say it helps them to forget their problems and make them relax, and some others think it is a fashion to smoke. (But I think this is silly).
Well, everybody should know that there is no good in smoking at all. It is really a bad habit. This habit will destroy their life, not only their life, but it also destroys the lives of those who don't smoke.
People who smoke should think of the effect of their smoking on others who don't smoke.