It's illegal to smoke in a car with under 16's in in some parts of the world
I'm not particularly anti smoking, if you want to smoke I dont care if you kill yourself. I do care, however, if you decide to smoke so it goes into my lungs and the lungs of my children. For that not to happen you have to be quite a long way away from me, so do it where I can't smell it
Lighting a ciggie, peeling a banana, unwrapping a sweet, changing a CD all fall within the distracted whilst driving a lethal weapon category IMO and, as said above, can see you prosecuted for driving with undue care and attention
On the subject on Taxi/cab drivers their license means they are not allowed to and many have been fined already