that's a good question but it's a part of human nature we do whatever pleases us right now not looking for the long term effects
I used to smoke cigarettes a lot almost 2 packs a day but now I am a quitter and that was as easy as it seems, the drive for me and many others was a mental one , you think of it as a little candy that you consume in your stressed times your free times and in-betweens once you get your thoughts fixed and determined, you will find that it's an easy decision that it' hard to take