Companies only do things for their bottom line, not for customer demand. Also, if nobody would buy gas from Shell anymore, their gas stations would just have to be rebranded to something else. Behind the scenes the oil companies are all trading with each other.
How I’ve learned it is, that cognitive dissonance arises when one of your beliefs or behaviours is challenged by new information. This can make you uncomfortable, and to alleviate that, people have coping mechanisms. It’s probably these coping mechanisms which cause other people to say you suffer from cognitive dissonance. There’s a quite good Wikipedia article on this imo.