Nicotine has several health and mental benefits and is not at all addictive if taken apart from cigarettes.
https://www.scientificamerican.com/article/is-nicotine-all-b...
https://www.scientificamerican.com/article/is-nicotine-all-b...
Let's put it this way: are there any scientific studies with results indicating that nicotine, by itself, has significantly stronger self reinforcing properties in comparison to caffeine.
The answer is no: there are none. Quite the opposite. Nicotine has pretty weak self reinforcing properties for all the hype. The magic is in tobacco smoke and various other drug interactions that result in the strong self reinforcing properties of tobacco smoke. So, when many people bring up nicotine's addictive properties they're really talking about tobacco smoke.
There's also the hand-mouth habit, but I digress.