I drink because I like it, although I do it in phases. Sometimes i'll have beer or glass of Henn everyday and other times i'll go dry for a few months because I feel like i'm spending too much money on alcohol.
I smoked nicotine because I enjoyed it and stopped doing it because I felt I was getting addicted to it and there was a noticeable difference in my lung capacity after a few months.
I smoked weed because I enjoyed it and stopped when my current job contract ended and I didn't want to ruin a possible job opportunity by failing a drug test.