Selection bias explains a lot of this. Smoking is easy to quit for most people, and ridiculously hard for most smokers. When I was 17-20 50% of my friends smo

Selection bias explains a lot of this. Smoking is easy to quit for most people, and ridiculously hard for most smokers. When I was 17-20 50% of my friends smoked cigarettes and 80% of my friends quit by the time they were out of college a year or two without any problems. The remaining 20% of my friends couldn't quit for the world. They've tried quitting 20 different ways and never succeeded. I think the difference is some people are just wired for quitting smoking to be hard, but most people aren't. And the former population is way over represented among the smoking population.