[Michael Ryan]

what is forbidden is always most attractive to some

[smellar]

Porn needs a taboo to exploit to keep pushing the buttons of consumers in an oversaturated market.
Decades ago it was rare to see porn include extreme anal or humiliation/domination, but it's been normalized now so it doesn't seem that exciting any more. Incest is just another taboo the industry can push.

[vinceslao]

I think a reason is the increase in "amateur" sites like patreon, clips4sale et simila.
Everyone can post stuff on there and with a low budget, topics like incest are easier to perform.
Imagine all the couples you see on pornhub... having amazing body is not enough, and after a while you have to start giving something more..playing with fantasies is the way to go

[RockTheBlock]

Just something to add to make it more forbidden in my eyes.

[mjpena]

Maybe because it's taboo?