It isn't just window managers, there are also applications that are close to X11, and many of these don't even work in XWayland, because they break wayland's se

It isn't just window managers, there are also applications that are close to X11, and many of these don't even work in XWayland, because they break wayland's security model. For example screen shot and screen sharing apps. And even if the developers took the large amount of work to refactor to work with wayland, there isn't any kind of standard for privileged access in wayland, so they would need to use different protocols to implement the functionality for each compositor.