I can write what I like to read for sure, but considering the subject matter I'm interested in is age gap between an adult and a minor, I can't just write whatever I want. I have to consider what I can write and what to omit. It's a delicate balance between my vision and people's expectations.
Other times, I just write because of reader demand, like my current story, which is not something I normally write. It was just an experiment to collect analytical data, so I thought of the most ridiculous premise I could think of, a girl who could not go to the bathroom without her male best friend next to her. I was testing out to see if a ridiculous title and premise would get people to get click, and they did, and they loved it! I predicted 10 chapters before I quit, I'm now in chapter 74, and it's about bathroom problems, a subject I don't care for, but hey, I might as well keep going and see it to the end.