Smoking is generally being viewed as dirty, smelly, and unhealthy by more and more people these days. Many people turn their noses up when they see someone smoking in their car or walking down the sidewalk, and it's often seen as a weakness in many ways.
So for social reasons it's not a good idea. It really does smell awful. I worked as a cashier once, and the worst part was having to talk to people who just came in from a smoke... the smell was just atrocious and I had a hard time being polite to those people, not to mention fighting my gag reflex.
Yeah, that's an extreme example and most people do cover up the smell very well but it's still not an attractive habit.
But in any case I think everyone knows the nasty side effects as far as health is concerned...