I was not a heavy smoker, but yes I smoked for about 15 years and quit a bit over 2 years ago.   Personally I was tired of being held is isolation from friends and family when I smoked.   I also got a bit angry that I thought smoking was controling my behavior and not the other way around.    But that's just me.    I do know it felt like a moment of calm in the midst of boredom, sometimes pain and sometimes it's just totally mindless.   I also got tired of the cost.   I imagine everybody has their own reasons.   It's not a good habit, but I can understand it.  

People know the risk and they still make the choice.  People ride without helmets, jump out of airplanes with/without parachutes, business men take adderall and live on caffeine. We can name hundreds of high risk behaviors, many of which might endanger the public.   How can a person who pays tax's to sustain the parks, then be denied access because of their particular habit?

Just saying.... I'm not endorsing smoking to anyone.