Nicotine's method of action for addiction isn't commonly understood very well. It's extremely specific - nicotine works to make the things you do around the exposure more habitual. If it's slapping on a nicotine patch and going on a run, you're more likely to get into a habit of slapping on a patch and going on a run. If it's taking a break outside and puffing from a vaporizer, then it's simply taking a break and puffing from a vaporizer.
That's largely why e-cigs are the most successful way to quit smoking tobacco products - it's the most similar habit to smoking cigarettes, so it slots into the existing highly-reinforced habits that smokers have. You drop a bunch of the random other chemicals that are present in cigarettes, and wind up reinforcing the replacement habit before dropping dosages and having a regular habit that's as easy to quit as, say, biting your fingernails.
Thing is, the fact that you can reduce the nicotine dosage does not necessarily mean that people will; unlike cigarettes, it's trivial to also increase the nicotine dosage many times.
I don't think a significant amount of people do that. Coming from someone with a lot of experience vaping (actually helped me quit smoking), it's somewhat difficult to find ejuices with pleasant flavors (anything that's not a stereotypical cigarette flavor like menthol) above 6mg, and around 9mg or higher, the nicotine flavor becomes quite pronounced and overpowering, and your flavor options are severely limited.
That's largely why e-cigs are the most successful way to quit smoking tobacco products - it's the most similar habit to smoking cigarettes, so it slots into the existing highly-reinforced habits that smokers have. You drop a bunch of the random other chemicals that are present in cigarettes, and wind up reinforcing the replacement habit before dropping dosages and having a regular habit that's as easy to quit as, say, biting your fingernails.