While nicotine is an addictive substance, studies have shown that many people are addicted to smoking because of psychological reasons. Getting over a nicotine addiction isn't that difficult but dealing with the psychological issues can be a challenge.
This usually happens with teens when they first begin to smoke. Under the effect of programming by their friends, they might believe that smoking makes them look cool. As a person ages he forgets about this reason but the addiction stays.
So many teens start smoking with the unconscious goal of rebelling against their parents, teachers or even the whole world. By doing an action that is believed to be wrong by most people, those teens rebel against the world.
So many people smoke when they feel stressed. The repetitive movements a person does when he smokes gives him a false sense of control. This becomes very obvious with people who light cigarettes as soon as they feel like they have lost control (when they experience anger, stress, anxiety...etc).
Many people smoke to serve the unconscious goal of appearing more masculine. This is also popular with women who smoke just to escape from the popular stereotypes people make about them such as the one that says that they are weak or overly sensitive.
Sometimes smoking starts as a result of peer pressure then after some time the person becomes dependent on smoking and fails to stop even after peer pressure is gone.
Even though psychological reasons are more complex and more difficult to deal with than nicotine addiction, the withdrawal symptoms of nicotine can still make it very hard for some people to quit smoking.
Some people smoke the most when they think about their problems. The feelings of numbness smoking gives helps those people survive. These people use smoking to escape from their problems or make the pain tolerable.
Because they don't tackle the psychological issues. In fact they may reinforce them. The teen who smokes to rebel against others will smoke more when he sees a health warning.
So many people start smoking because breaking the rules gives them some excitement. Soon, those people get hooked and find it hard to stop.
So many people describe cigarettes as their friend. Some people say that they feel less lonely when they light up.
Some researchers have said that smoking is analogous to thumb sucking. A smoker can smoke when he feels tense and when he unconsciously wants to take a soothing action such thumb sucking.
If a person wants to get closer to someone (or a group) that already smokes, he might start smoking, mimicking their behavior. People spend more time with those that are similar to them.