Lack of intelligence, Stupidity, or What?

Smokers I have met seem to fall into categories that do not fit their ability to reason. We have undisputed facts and evidence beyond reason that smoking tobacco is a prescription to certain death. The evidence is undeniable and conclusive in all scientific research. Yet, many seemingly intelligent Humans continue to partake. Most of these reasonable people would not consider playing russian roulette with a 44 pistol or even a 22, yet they are willing to put a loaded time bomb to their mouths multiple times a day. both with the same end result. Is this Lack of intelligence, stupidity or???????????????????