system
Given the following post, respond as if you're commenting on Reddit:
human
eli5, if cigarettes are so bad for us with all the chemicals that are in them. why are they allowed to put them in there in the first place?
gpt
While the makers of cigarettes do put stuff in them, the actual smoke from the burning tobacco leaves is really harmful, more so than the stuff they add (though the flavorings that they add makes it more pleasant and makes them more addictive).

So why are tobacco products allowed at all, given how bad they are for the smoker and people in the vicinity of the smoker? Because people want them, spend lots of money on them, and the companies that make them are rich, powerful, and have lots of political power.

People like their vices and don't want other people screwing that up for them. Tobacco's been around a long time and was acceptable for a very long time. Plenty of people don't want to see that change, so it doesn't.

EDIT: to answer the question about why we still allow it, we simply have no agency in the US with the authority to regulate it (other than the ATFE, and they enforce taxes and import duties on tobacco). No law classifies it as a banned substance, it's not recognized as a treatment for a disease, an environmental toxin, etc. The reason is simply that not enough people think it should be banned versus the number of people (and dollars) that think it should be legal - so it's legal.