Addiction is a condition that results when a person ingests a substance or engages in an action that can be pleasurable but the continued use/act of which becomes compulsive and interferes with ordinary life responsibilities, such as work, relationships, or health.
People first of all start smoking or drinking because of peer pressure, home influences, just to get high, and so much more.
It's not that it actually takes your bad feelings away, because it does for a small amount of time, and then it makes you feel even more depressed than you were before.
Which would then mean you will take in more so you can keep feeling on top of the world and not more and more depressed.
When people get addicted, they don't exactly know what they are getting into. For all they know, they could be gradually approaching their death. People can try to stop the horrible action. But what good does that do to the smoker when they have already gone deep into whatever drug they consume. The only thing that will make them change is the realization of how bad smoking is, and what it can can do to someone.