I will say, just because it costs them more money doesn't mean they should legally be able to act on that.
Many times someone from a certain religion might cost an employer more than someone who doesn't need religious prayer breaks. But legally employers can't act on that.
I'm not saying smoking = religion, but I am saying information available to make logical decisions != the ability to act on that information. Just saying we've already made the decision that we will legally restrict companies from acting on certain pieces of information and therefore we can expand this existing framework to protect other life choices (eating fatty foods, skiing hobby, driving a sports car, having kids, etc)