I can understand it can be hard for someone to quit smoking. However to smoke in a closed confinement, such as a car, is really something we should try to watch out for. When driving alone, there is noone you need to consider. Once someone in the car, the person next to the smoker as NO choice whatsoever other than smoke the fumes of the smoker.
Some smokers say : I don't force you to smoke, so why should you force me to stop smoking. Truth is : when standing next to someone smoking, this person is giving you his fumes. Thus forcing you to smoke. If you are standing outside, you can always find a space away from where the smoke is blown to. But inside is another story. Inside smoke stays in the same room, actually this smoke is even more harmfull than the original smoked inhaled by the smoker.
Since I've never really smoked, I can not talk about the quitting. Though I comprehend this can be very hard for someone who smokes daily. My father used to smoke untill he was hospitalized for a hip operation. During his recuperation, there were a few weeks he could not stand up and go for a smoke. This is how he quit smoking. So I guess if people really want, they CAN stop.