I don't want my property smelling anything like smoke. Smokers don't exactly get it because they smell like that all the time, but that smell lingers and it's simply gross. Not to mention over time the smoke will yellow anything that is remotely white including curtains, walls, furniture, etc. And who wants to deal with cigarette butts everywhere? (or a bunch of them sitting in a bottle on your porch, ewww!)
In my listing I make it clear no smoking or vaping anywhere on the property, inside or outside. I write that "If you smoke or vape, another property would be more suitable to your needs."
And vaping isn't harmless. It produces a huge cloud of white smoke that stinks! Yuck! I don't want to breathe in the huge cloud you just exhaled!
Not allowing smoking/vaping shouldn't be considered unreasonable. It's simply another rule like any other you want to implement. It is YOUR property, afterall, and your rules should be respected.