When someone smokes in your home you are exposed to second hand smoke via clothing and other items. Your health will increase if you are no longer exposed to hazardous conditions.
They have a lower chance of second hand smoking, which is one of the leading causes to lung cancer for non-smokers. Also if given the fact that the smoker is a spouse, they won't have the price to smoke regularly taken out of their shared salaries. Finally above, if the smoker was to quit, they have a a greater possibility to live longer, refrain from injuries (such as removed limbs, the falling out of teeth, cancer, a stoma being placed in their neck, the discoloration of teeth and nails, excessive ageing, ect.) and there forth saving the individual from mutual emotional stress of dealing with a known, or loved one going through the possible side effects in the future.