There are many reasons why smoking should be banned in all public places. The most obvious is that it is unhealthy for the smoker, as well as everyone else near the smoker, especially in closed areas. Undisputed scientific studies emphasize that second-hand smoke is almost as medically hazardous to exposed non-smokers as it is to the smoker. Smoking is more than a habit; it is an addiction, and every step should be taken to discourage people, especially the young, from becoming addicted.
Children, chronically-ill people and the elderly are the most vulnerable to second-hand. It just takes a little longer for non-smokers who are exposed to develop the same ailments, including chronic throat and mouth irritation, emphysema and other lung problems as the addicted smoker.
Another reason smoking should be banned in all public spaces is that it is unpleasant to non-smokers. Where it is permitted in restaurants, bars, casinos, theaters, transportation and other places, it is simply that the inconsiderate smoker is imposing his/her addiction to the discomfort of others. If those persons must indulge in smoking, they should do it in designated indoor and outdoor areas where it will not annoy and/or sicken others.
As a personal note, during most of my working years, smoking was permitted just about everywhere. Except for showing off at age 13 by smoking an entire pack of cigarettes and getting very sick, I've never smoked since. However, until the era of banning some areas to smokers, I had to endure the annoying smell and discomfort in restaurants, theaters, airport lounges and many other places. When I attended business meetings in small rooms, i always had to hang my clothing out to air after I went home. It wasn't that I was allergic, as many unfortunate people are. I just found the smell of burning cigarettes, the breath and clothing of addicts annoying, their attitudes inconsiderate.
We who survived the many years before smoking in public places started to be banned are thankful that medical studies exposed the obvious. They proved that cigarettes are deadly to both the smoker and everyone else who must involuntarily be exposed to them. Of course, the medical studies revealed nothing new. As far back as the early 20th Century, cigarettes were called coffin nails. It's just that people finally woke up to the facts of the deadly consequences of smoking, and realized the culture created to enhance the profits of the tobacco companies was simply wrong.