Maybe people don‘t because they see, for example, Valve (a billion dollar company) struggling to get GNOME to implement drm-leasing for VR headsets. IIRC they‘ve been at it for multiple years, too.
Or maybe it‘s because the compositor developers are not exactly concerned about ease of development.
To quote a GNOME dev[0] about support for the aforementioned drm-leasing protocol:
> I honestly don't have a problem with forcing clients to implement the portal if they want to work on mutter.
I wouldn‘t blame the people who choose to simply not engage with that process, especially those who work on these things in their free time.
[0]: https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2759