I think more plausible explanation is just plainly not many companies wanting to put their ads on porn, so hosting porn is significantly less lucrative per viewer than SFW content
and then , i remember back in the days of TV there was soft porn or adult talk shows on TV late at night. They did have ads, and not the cheap kind (cigarettes, alcohol etc). TV was somewhat self-correcting, because kids are usually asleep past midnight so the ads matched content . On the internet it's nigh impossible to keep kids outside of content, so maybe that's a reason why adult content is unfundable and why the default for censorship is to make everything kid-safe. But maybe there is a way to make that work, i dont know