What website, whose revenue comes from engagement and engagement from content, is going to do that?

And more importantly: it doesn't matter what Pornhub.com does. If they develop ethical scruples, another site will simply spring up to serve that supply and demand. Like a gas, the market will expand to fill the legal space available to it.

There is some truth to this idea, but it doesn't trump all other dynamics, always. These markets can have their structure changed by evolving cultural effects / morals / etc.