When I was a student I asked for an instructor change because I was sick of my instructor stinking of cigarette smoke in the C152. At one flying job interview I have been to, I was asked straight up if I smoked ... I said no ... and my interviewer said good, he wouldn't employ a smoker.
It's just not a good look for instructors or any pilots if you ask me, and you can certainly put a lot of potential customers off from an instructor's point of view if you reek of smoke all the time.