It’s tightly interconnected with accessibility because alternative input systems, like eye gaze input, macros to expand text, and other accessibility tools for alternative input hardware all friends in the same types of window-agnostic input interacting. (Similarly for output hardware, I think?)

Like, custom text replacement with XCompose breaks because of how Wayland “silos” programs, which is why ~/.XCompose files only partially work in KDE Plasma. If Wayland/KDE fully implemented accessibility tools, then it would be possible to solve all of these problems.

Or, at least, that’s my layman’s understanding of the situation.