A big security advantage of Wayland is not allowing applications to read input devices all the time. Having /dev/input/* accessible to the user account subverts this advantage.
libudev-devd was opening the evdev devices to detect their types (mouse, keyboard, touchpad, etc). This does not work when /dev/input/* is inaccessible.
With the kernel exposing this information as sysctls, we can work without /dev/input/* access, preserving the Wayland security model.
p.s. would be nice to see this MFC to 12