[Z]

Probably because smoking is the most irritating of the lot. It sticks to your clothes even if you yourself aren't smoking, it sets off asthma, it irritates your eyes (like any type of smoke) and it's seen as a surefire addictive habit, whereas alcohol and eating unhealthily are seen as more controllable vices I guess? You can run off calories and you can drink tap water to flush out alcohol, you can't get rid of tar in your lungs.