Most probably brand recognition and or copyright protection, like half the videos on porn sites aren’t uploaded by the original creators, just illegal rips, so it probably helps them with takedowns and shit.

If there were better copyright protections for porn, they wouldn’t feel the need to watermark their stuff.

Plus you gotta treat only fans as the independents they are, you can’t compare the big tiddy goth girl on only fans to Netflix, they’re nowhere near the same.