Yes, what you say is true, but we could carry the anti-smoking madness to heights you don't even seem capable of comprehending.
You're not getting the free market concept. Employers make hiring and firing decisions based on the profit potential of those decisions, in the same way that you make investment decisions. If private employers make the mistake of limiting their employment pool to such an extent that they've weeded out all of the drinking, smoking, fast-food-eating, laundry-washing, tooth-brushing, and hair-combing candidates, how do you expect them to stay in business? There's a reason why business owners make a lot of money, and it's not because they're stupid.