An organization can't outwardly support it because that would be a legal nightmare once participants get hurt or die as a direct result of it. They may also struggle to get events sanctioned by the jurisdictions that they're hosting the events in.
That said, there are plenty that turn a blind eye to it as best they can, as others have pointed out.
Why do people watch movies when books exist? They're different mediums for delivering a story.
I saw this thread and assumed you were talking about actual walking simulators like Firewatch or Gone Home, ones that don't really have any gameplay mechanics besides walking and interacting with objects. But from your comments you seem to be taking issue with games like God of War, The Last of Us and The Witcher which makes me think you're a little misguided as to what those games really are. Those games have a story but that's not the sole reason they're popular. They're all groundbreaking titles in their own right from a technical perspective, they just happen to have good stories because that makes them resonate with players even more.
It's like how a movie with a bunch great fight scenes and no story isn't going to resonate with audiences in the same way as a movie with great fight scenes and a story to tie it all together. It's an important part of the immersive experience for a lot of people.