Smoking Addiction is a Result of Deeper Troubles

I was at a party last weekend, and the girl I was sitting next to was just going through her third (or fourth?) cigarette. As she inhaled and exhaled the smoke, I started to wonder about why people smoke.
Having smoked more than a few cigarettes myself, my curiosity also probed into my own actions as well as the larger societal picture.
Everyone knows that smoking tobacco is bad for your health, but why do people still do it? There is a strong correlation between smoking and various forms of cancer, yet that hasn’t stopped many from quitting the habit. Long-term smoking also causes teeth to yellow and the smell is irritating to many people, yet smokers obviously don’t mind.
I believe people smoke (and continue to smoke), not only because it is an addicting habit, but because they want to damage their bodies in order to compensate for any unhappiness and/or stress in their lives. Cigarettes are saturated with nicotine (proven to be an addictive ingredient), but that doesn’t explain why some people only smoke a few cigarettes a day and others smoke a pack a day.
In my opinion, smoking tobacco is a self-abusive behavior.
Smoke, in general, is a waste product and pollutant. Smoke is directed away from living environments through chimneys and excreted into the Earth’s atmosphere by factories, because no sane individual wants to be in an environment where the air is polluted and not breathable.
If this is true, then why would anyone actively feed pollution into their body through cigarettes, where the smoke is being absorbed by their lungs and body?
It is my personal opinion that subconsciously (and perhaps for some it’s conscious) smokers know that they are taking in pollutants, and they know that these pollutants are hurtful to their bodies, which is part of the satisfaction of smoking.
Individuals who abuse themselves get satisfaction from the pain of the abuse, but with smoking, I believe the ‘pain’ is the knowledge that smoking causes the body to eventually deteriorate and the fact that it is just unhealthy in general.
Causing certain types of harm to oneself usually satisfies unhappiness or stress.