You could drive a semi through the gaps in this report in the Guardian about research on movies and smoking. I’ll ignore all the silliness in reporting, research design and drawing conclusions.
One of the reasons that film makers like to put cigarettes in movies is because the smoke is so much fun to film. Tobacco smoke has this wonderful interplay with light and shadow that looks great on the screen. That’s not a reason to put a cigarette in a scene, but it’s very tempting to use smoke when it might seem appropriate. On the other hand, the visual appeal of the smoke does add to the glamour of the habit. Maybe film makers need to look for every opportunity to burn dried leaves and grass.