Stop in for a cup of coffee

So question to the smokers on here, if you are in a designated no smoking area why do folks think the vape, E cigarettes inhaler looking rig is acceptable? Forgive my ignorance not sure what the rig is called? Question two, they are deeply offended when you ask them to stop or go somewhere else, invariably they respond “I am not smoking”. I would love some advice on how to handle it so that I do not offend a customer. My method thus far has clearly been far to aggressive.