Generally, core Wayland is very minimal. It's meant to have only the pieces that are essential for every Wayland implementation, not just desktop window managers. Therefore you have xdg-shell extension which is meant for desktop and its windows, you have ivi-shell which is meant for automotive applications and you can have your own extension if your use case is different enough to need it. Thanks to that, KDE and GNOME don't have to implement any IVI stuff and cars don't have to know how to minimize or maximize a window, which, as a concept, might not even really exist there.