Unity and Mir were ready and usable years before Wayland was usable in practice, though. It's still used on Ubuntu Touch because it allows for reuse of the existing Android graphics acceleration stack in a way that Wayland doesn't.

Canonical often invents things that other parties like Red Hat then reinvent, often learning from the mistakes Canonical makes, leading to a better end result for everyone. I dread to think what systemd would've looked like had upstart not laid the foundations for a normal service management system on Linux.