Joking aside, non-smokers should not have to pay the insurance costs of smokers. It is all fine and good if you want to do that to yourself, but you should also have to pay for it. Simply not hiring smokers is the right decision, they dont get tangled up in the details of sorting out what diseases stem from smoking and what are natural.
It's different paying for insurance to cover incidents or conditions that people can't control (accidents, genetic diseases), or would be bad for society to not cover (pregnancy, psychological issues).