If I started smoking, it would be because it's bad-ass.
This would be a common answer, wouldn't it? Peer pressure. As much as we hate cancer and cigarette addiction, something has been engraved like an unspoken rule. If you smoke, you are cool.
I think it starts with fantasy. I'm a fitness and health nut because I want a body and long-life like I see in fictional and non-fictional materials of movie, comic, cartoon, etc. I'm striving for an awesome and attractive future "me". A lot of us do this today, but it goes both ways.
As bad as smoking is, so many of my favorite (fake and real) characters do it. It's a trait they share, this "I don't care, it's me". "Being comfortable in one's skin (and mortality)" meaning confidence and integrity. Drugs, alcohol, smoking, and partying (all attributes to "cool") can all be a future "me" if I choose apply myself to them.
Will I though? I won't make that decision yet. But I know that it's bad-ass.