Yes it is, but its artificially added in varying doses to cigarettes... you are not just getting the natural nicotine from a tobacco leaf when you smoke a commercial cigarette.
You aren’t bursting any bubbles, just are ignorant of commercial cigarette production or willingly witholding facts.
It is not so much that it is “added” as opposed to being concentrated either more or less during the curing process. Even the home grower who processes their own tobacco is capable of changing the nicotine levels of the end product. Additionally different types of tobacco have different levels of nicotine concentration in the plants themselves.
I assure you, I am neither ignorant of commercial production, nor willfully withholding information. There are quite a few of us on this forum who have extensively researched the processes into tobacco production and processing.
BTW, I don’t smoke commercial cigarettes, and have not done so for close to 10 years.