I know what you mean - and I agree, but your logic is sort of flawed. That is like banning garbage because people litter. You really should go after them for littering then, and make littering a harsher punishment, especially if it is cigarettes they are littering.
It is not just unseemly or environmentally unsound, it also can pose a real risk of fire, if they just flick the cig still partially lit onto the grass. Some people really are irresponsible. I won't say stupid, but they just don't care enough.
Maybe if they burned their own house down by doing it, they'd care more.
Actually I did not call for a ban on smoking in parks. I was simply pointing out that the noxious habits of many smokers makes them an easy target. As for garbage, I thought it was already banned in terms of tossing it anywhere one wished. BTW I dislike being around smokers so much that I won't even make friends with one of them in order to avoid having to tell them to butt out in my presence.