Being a life-long non-smoker I've sometimes been in a situation where the person servicing me has just had a cig. "HHHHWhat cHHHHan HHHHI do HHHfor HHHHyou, HHHsir?" -Please, could you stop breathing and change your clothes after you've had a proper shower...
Don't get me wrong, though. There are smokers and there are smokers. Even at school I often spent the breaks with the smokers behind the corner and have been continuing the habit at parties where people go out for a smoke. No way for me going into a dedicated smoker's room, though.
But when dealing with customers or patients, you can never tell whether the next one is heavily asthmatic. No smoke, no perfume, no pet hair/dust in your working clothes may save your job from a million dollar sue.