The science behind why it's so difficult to quit smoking is crystal clear: Nicotine is addictive – reportedly as addictive as cocaine or heroin.

Yet any adult can stroll into a drug store and buy a pack of cigarettes, no questions asked.

"From a scientific standpoint, nicotine is just as hard, or harder, to quit than heroin …

https://www.heart.org/en/news/2018/10/17/why-its-so-hard-to-quit-smoking