I think this is easy: A teacher wants to earn money!
But anyone can self-teach piano without a teacher. You need 3 things:
- Methods Books / Sheet Music for your level
- Tutorials / Lessons on YouTube
- A forum for hosting specific questions
About 1, teachers are neutral. They use method books for their own teaching, and they know this is out there.
About 2, teachers are using them as advertising, mostly. You get some very basic tricks, here and there on a specific topic, but very often if you want to go deeper, you find a link to a paid online course.
About 3, teachers hate them! 1 and 2 need from time to time that the student can address some specific questions. And to do this, the best place is a teacher. A paid teacher, of course. And a forum is cutting down their income in a certain way. So don't expect teachers to contribute here.