Why do they sell cigarettes at gas stations?

Gas stations began as small community stores which JD Rockefeller convinced to carry gasoline even if they had to wait years or even decades before they made their first sale. That's the reason gas beat out electric cars when electric cars actually evolved before gas cars... he got the fuel to the locations where automobiles would one day travel to. The reason we have fossil fuel cars is Rockefeller understood how to sell gasoline and almost from the start, electric cars failed because they were designed poorly and the auto industry became dependent on fossil fuel expecting the government to pay the full cost of any conversion to alternate fuel where they wouldn't have to pay the cost... under Obama, they were paid enough to create a few electric cars but his investments in solar and other energies totally tanked costing taxpayers hundreds of billions of dollars which is why past Presidents were wise enough not to do this but to encourage the private industries to try.

As for your question.

Technically, these places aren't gas stations but convenience stores. If you notice, most don't survive where there's not a lot of traffic or they don't appear to make a lot of money. Convenience stores target traffic and where they think traffic will be, that's where these stores will be built. Some only offer a few snacks or cold drinks, some offer showers and motel rooms... but they all sell gas and cigarettes because people smoke heavily while driving and often run out so they stop at convenience stores to grab cigarettes because it's convenient for them to do it.

There's your answer... convenience.

While it sounds stupid to sell cigs around explosive fossil fuels, it is far more dangerous to talk on a celphone while fueling or to leave your engine running... even putting the gas nozzle into your tank to fill it up is more dangerous than cigarette smoking.

As has been proven on many shows like Mythbusters, tossing a lit cigarette into a bucket og gas or on the ground where gas has been spilled will not ignite the gas, the cigarette will simply be smothered out... it's a Hollywood myth for the most part.It takes a spark to ignite gas and while a lit cigarette can burn you and produces heat, it's not a spark or a flame.