Why do some people who smoke live well into their 90s?

For the same reasons that some persons who don't use seat belts never die in auto wrecks; and others are obese, don't exercise, have unhealthy diets, yet don't die of heart attacks. Nobody ever said all smokers die early. Some people may be differently sensitive to the adverse effects of tobacco, but mostly it's just random chance. Same for seat belt use, poor eating and exercise lifestyles, etc.

The same DNA that some alcoholics have that don't come down with liver cancer, or heart attacks from no exercise or obesity. Smoking can cause COPD and other problems but many live a long life. There are many who don't smoke and die from lung cancer, why?