Ah ok, so from that perspective there _could_ be someone for which heroin is not addictive. That makes sense, although I don't think that this is the definition that most people use.
https://www.jrf.org.uk/sites/default/files/jrf/migrated/file... is a very small survey of heroin users, some of whom report controlled or occasional use.
https://www.drugabuse.gov/publications/research-reports/hero... shows that with 90K-170K new users per year from 2006 to 2016 resulted in 600K total dependent users in 2016 in the U.S., so not all first-time users become dependent and presumably the 2016 count includes people who tried heroin for the first time before 2006.
https://www.cdc.gov/drugoverdose/data/heroin.html confirms that the difference in new users and final dependent users wasn't all due to deaths, either.
There's still a possibility that only rehab keeps people from becoming dependent but the numbers are harder to find for that.
Meanwhile, I've only met one person who has been able to use cigarettes occasionally (a few times a year). Everyone else has been at at least a daily smoker, and while I know quite a few people who have successfully quit, it's almost always been a rough experience with multiple attempts required before succeeding.
If cocaine and heroin were legal and cheap, I'd probably be more concerned if a friend took up smoking than either of them. Conversely, if cigarettes were illegal, I'd be really concerned if a friend took up smoking.
Well, there is also selection bias: you assume people like this just don’t smoke. I enjoy smoking, but I don’t smoke, and there was no problem for me to stop. There was some research that some percentage of population genetically is not pre-disposed for smoking addiction.