All is driven by pleasure or pain.  The need to derive pleasure and avoid pain are instinctive, even visceral functions like getting up in the middle of the night to go to the bathroom.  It is all part of the pleasure / pain syndrome.  This is part of our make up as human beings.

If quitting smoking is a painful process, it will be difficult to stick with.  Why do you think only 5% of all smokers actually quit without any help?  We will go to much greater lengths to avoid pain than we will to gain pleasure.  This is also why people try nicotine gum, patches and inhalers.  This not only doesn't work, it merely replaces one habit for another.  One of the keys to quitting smoking effectively is to minimize the pain and enjoy the process along the way.