It's because this feature was implemented as a pseudo-keylogger on X11. All X clients could listen to the compositor state at all times (including input), even if input was focussed on another (potentially sensitive) application.
In Wayland, clients have almost zero knowledge of the compositor's state. This was an explicit design choice to enhance security and enable modular features via wayland protocols. Of course, this also killed every implementation of app-specific global shortcuts.
Wayland protocols take a lot of time to get agreed on - They need multiple implementations across different compositors (usually means KDE and GNOME need to implement the protocol spec and agree to it) and the specs can take a long time to design and reach production.
Obviously this does hurt uptake for Wayland since issues can take years to resolve, but the core team are very aware of the pitfalls of X11's development and have long preferred this slow and methodical approach in the hopes it's sustainable and maintainable into the future.
you might wanna add a swapfile. A slow desktop is better than a crashing desktop!