It's about competition, heathy market and legacy. You can't have that with formats like OOXML. Deliberately so.

I can't find the story, but I think it was of the British library, trying to recover documents in very old Microsoft Word. They had to chain together VMs of old Windows with old Word versions to get it the documents to the modern world. Formating will have been mangled of course.

That is how it is with proprietary "standards". It's like ensuring today is a digital darkage.