People take up smoking for all kinds of reasons. Not all become smokers; I have known lots who only smoke when they're at a party, or a bar, or only when they're stressed, seriously stressed. They take it up for a night, or a few weeks, and then they put it down again and go on just as if they'd never smoked. No muss, no fuss. I don't understand it, I've just observed the phenomenon.
If 18+ kids take up vaping, without first stopping at the cig-addiction booth, I'm okay with that. It is the place of their friends and family to raise objections to that or any other pastime, not mine as a stranger. Vaping qua vaping doesn't hurt bystanders, and that's where I think society should draw the line when it comes to caring what strangers do. (Polite behaviour is another matter, I'm talking about codifying legal restrictions on personal choices.)
Self-medication is a murky subject; most of us go about it without conscious thought. When my body is jonesing for greens, all I can think about are salads. I don't set out to market thinking, "Today I shall eat lettuce, and perhaps green beans, for I am in need of anti-oxidants" or whatever it is that greens provide to keep things ticking over internally. I used to head for cigarettes when I wanted to think, now I pull out my PV. I used to, when undergoing bouts of total abstinence, get crazy and scattered and sad unto weeping. Now I've got this lovely vapy stick, and poof! no more with the cigs, no more with the sad. Someone might say, "Ah, but if you'd never taken up the cigs in the first place, it wouldn't be such an ordeal now." To which I respond, bollocks. I remember what I was doing. I was prowling the halls of the dorm, I couldn't settle, couldn't rest, or think. I finally went out to the corner store and bought a pack. Instant relief, followed by hours of productive study.
Tell me how bad nicotine is for me. G'won, cite studies, draw charts, knock yourself out. I was a smoker for 35 years, I've been there, done that, and I own the t-shirt factory. Nicotine may be bad for you, but for me? it makes my brain work. I'm just happy to have found a way to get it that also doesn't make me feel infantilized or put to shame, the way gum or patches do.
I expect people will take up vaping who are not in fact users of tobacco products. I expect they will do so for all the reasons people take up tobacco now. Some will continue to vape regularly, some not, just like now. People are complicated. They don't all do things the way I would, or the way you would. On the whole, they seem rather fond of their own solutions.
Frankly, I'd like to see vaping cheap, easy to master, and readily available.