And Apple doesn't really want to anyway, they get to profit from both side this way.
The iPad could be a fantastic machine but as is, it makes no sense for most workflow. It seems to be stuck at being a fancy notepad or expensive drawing tablet for hip artists (real pros use the much larger and more convenient Wacoms anyway).
iPadOS has certainly got a lot better over recent updates, but there's no sign of 'apps' catching up with serious desktop software any time soon.