Maybe because it's 'forbidden' or because you think it might be a way to fill a void? They seem to comfort those who smoke them, so they can seem appealing if youre seeking comfort. (Especially if your go-to methods of comfort - eating? Drinking? - aren't working for you anymore.) Paradoxically they're almost a form of self harm - a rebellion against the consequences, 'I don't care anymore!' I guess those are some of the reasons why I bought a packet of cigarettes earlier this year. The first packet I ever bought in my life. I smoked 6 or 7. They did squat.