Youbebetty, everyone takes calculated risks, but in their calculation is the thought "it can't happen to ME." This includes not just smoking, but also that other dangerous pursuit, sex, which of course can kill you or get someone knocked up, no matter how many precautions you take. Driving is incredibly dangerous yet most of us do it. So it's not ignorance -- most people know what the risks are -- it's irrationality.
Jaguar, that's cool about SIGIT. I got several Christmas greetings from Indonesians who were Muslims. One of them, who wasn't sure what religion I was (I'm not a religion, but they don't understand that, so I always answered with some vague answer) sent me a Rosh Hashanah card!