My guess is they’re realized documentation is a huge cost center and even their own technical writers are overburdened by the churn of deprecating APIs and changing best practices. It’s worse then the JavaScript community.
It was one of things that I found unbelievable when switching from Android to iOS development. The developer experience is just so much WORSE on iOS. Sometimes, it's as if Apple is actively trying to annoy developers.
It's a tiny cost center, in the grand scheme of things. As it is they probably spend less than they spend cleaning the glass at Apple Park.