1 reason I can think is kinda the same thing with Vulkan. They both are so agnostic to what they run on that they have a minimal set of things that they function with.
In the case of Vulkan its: I interact with the graphics processor, and don't care if you have a display so windowing is an extension and has platform implementations if applicable.
And in the case of Wayland its: I am a protocol for managing and displaying windows, and I don't care what kinda inputs you have (example: VR doesn't have classical PC inputs).
In the case of Vulkan its: I interact with the graphics processor, and don't care if you have a display so windowing is an extension and has platform implementations if applicable. And in the case of Wayland its: I am a protocol for managing and displaying windows, and I don't care what kinda inputs you have (example: VR doesn't have classical PC inputs).