Wow! How does nicotine affect the ability to do any job? The only one I can think of is in the case of withdrawal. That is insane and this comes from an avid anti-tobacco person, is a legal substance. If I were to be fired for having caffeine in my system, it would be as ridiculous.
Alcohol and pot can affect behavior and actions and reflexes etc.
Simple.
The companies made deals with their health insurance providers for lower premiums
and they made “no-nicotine” a condition of employment.
Smoke, chew, dip, chew nicotine gum, wear a patch, use an E-cig...
...you’re outta there.