It's the mental addiction. The physical health is not really something you deal with every day - usually doesn't get super serious until you get older. But when you are addicted to smoking (cigs or ecigs), it changes you. It interferes with how you live your life. You are now thinking about smoking a lot, when the next time you smoke will be. You will be doing something and then you will think "I wish I had a cigarette" and then that will consume you until you find one. You are less productive because of this. You are less in the moment because of this. You become controlled by the addiction. To me this is much more serious. You might die 10-20 years earlier, sure, that's bad, but if you aren't living to your greatest extent right now, I think that's much worse.
I actually think ecigs are worse than normal cigarettes for this reason. It's now socially acceptable to smoke them, easier to smoke them (you can just hop into a bathroom stall and take a hit).
In my personal experience, vaping does not feel very addictive at all. I used to be a heavy smoker, using 3-4 hand rolled cigarettes every hour unless I was somewhere I could not smoke. I'm now a heavy vaper, I vape all day every day, but it feels more like something I do because I enjoy doing it than because I need to.
When I was a smoker, running out of tobacco would induce panic attacks. Every minute spent on an airplane or at the movies I'd devote most of my thoughts to longing for the moment I could have a smoke again. When short on cash, I'd prioritize tobacco over food.
As a vaper, I have on multiple occassions forgot to bring my vaporizer (or charger, or e-juice) when travelling and gone without for days with no problems at all. A bit annoying perhaps, but no more than forgetting to bring my headphones before a flight or something like that, certainly not even close to the cravings I'd get when I couldn't get hold of my precious tobacco during my smoking days.
There's obviously individual differences at play here, but if someone came to me complaining about their horrible vaping addiction I'd have to restrain myself from not going all Bob Saget in Half Baked on that poor vape junkie... ( https://www.youtube.com/watch?v=LEberTUvrsE )
I've never smoked, but I agree with you on the vaping not feeling very addictive. I vape all day while I'm working (I work from home), but I don't take my vape with me when I leave the house, and while I occasionally have a thought like, hmm, a vape would be nice right now, I never feel driven to vape or deprived without it, even when I'm out of the house without the vape all day.
I actually think ecigs are worse than normal cigarettes for this reason. It's now socially acceptable to smoke them, easier to smoke them (you can just hop into a bathroom stall and take a hit).