Caveat: I've never smoked or vaped, but I have plenty of friends that do both.

I think the idea is that when vaping, you are able adjust the level of nicotine you are consuming without having to adjust how often you engage in the physical act of vaping/smoking. The act is a comfortable ritual, a chance to take a break, step away, relax for a few moments, whatever. It's a habit itself, distinct from the nicotine dependency. Quitting smoking is doubly painful if you are craving both the chemical and the act. Vaping gives you the act without the chemical.

This doesn't even touch the fact that nicotine is not particularly harmful - simply a habit-forming stimulant like caffeine, adderall or modafinil. Vaping delivers the nicotine without the tar, and the tar is what kills. The thing that makes people nervous about vaping is not the nicotine, but the behavior of the (largely unstudied and unregulated) substances in the vapor being inhaled.

Indeed. Stimulants tend to form habits. It's not as noticeable with caffeine, because there is a 15-60 minute lag time for it to take effect. Nicotine (largely due to the delivery method, I assume) takes effect in 10 seconds. So it's easy to start forming associations with the feeling, leading to the psychological dependence.

One other point I have yet to see mentioned here that occurred to me when I made the switch from smoking cigarettes to vaping several years ago is that vaping also changed how I engaged in my smoking ritual.

A cigarette has become a somewhat expensive object. When I light it up I would finish it, or at least try to. If the time I had for my smoke break was short I would puff that thing hard to get it done in the time I had allotted. An e-cig can be used for a few puffs and then dropped back into my pocket with nothing wasted. I could be much lazier about how I smoked and as a consequence I tended to smoke less.