It's a cheap/easy source of assets for someone who wants to tell a story. Games like The Company tried to move away from RL porn images/clips and supporters rejected it, because they like the result.
The games with real porn made of screenshots from porn videos lacks consistency, the MC is not always the same actor, so it breaks the narration.
Making a VN with real actors could be possible only with big earnings, because many people will be invlved. So it seems difficult to be achieved for a new project.