Ultimately, Humankind have to rely on the evidences and rigors of Science.
At the least, you had admitted that the two you knew quit smoking and vaping.
Nicotine does not turn Humans into Zombies.
Only VAPING DOES, as although it is only laced with nicotine without the tar, Kpods are only the INITIAL aims of drug lords and their executives in the Trillion dollar enterprise to get Humankind HOOKED to hardcore psychotic drugs in later stages, as found out recently that such Kpods, even so called from established sellers, had induced Epitome, more well known as Fentanyl which mostly came from China, had proven to wreck American lives turning them into addicted zombies than they, an intelligent civilization were destined for.... .
Drug lords, too, play the long game as they have Billion$ to spend for best minds, as they saw how Humankind had mostly gone against their deadly products and the dwindling of their profits - cars, women, luxury homes, vacations, etc, at the expense of misery of and to others.
If vapes can have multi-flavors such as chemically created strawberry or even durian, how MORE easily is it to introduce other chemicals such as hardcore drugs, let alone proven currently used fentanyl, such as heroin, weed, cocaine, etc???? Thailand's dance with cannabis had proven that just a few drops of such even to a Kangkong/Spinach dish can either get one addicted or have hallucinatory and even health harmful side effects....
IN THE END, it is about MODERATION.
Humankind needs to live. We can BAN everything and live life like Buddhist monks, or the much twisted religion of Islam from Arabs which is NOTHING akin to what the good prophet Muhummad had taught, foreswearing everything to achieve Nirvana.
Without bad, none would know what is good. Sadly, it is only thru mistakes that Humanity will learn, and change its ways.
There are chemicals which when taken in moderation does no harm, but only when taken in excess, it not only harms oneself, but loved ones and society as well.
As for WELL KNOWN hardcore chemicals such as fentanyl, heroin, weed, 90% proof alcohol, etc, etc...only morons will want to commit suicide, and worse, misled by profit seeking peddlers and influencers, for their own unnecessary demise.....