Xwayland makes use of legacy features of X. If we were to compleately drop all aspects of X tomorrow, the Linux desktop would essentially compleately break and become unusable.
The fact is, at this point in time after 10 years or more of development, Wayland is still very much in a state of perpetual beta. At this point in time, and for the foreseeable future, Wayland involves compromises that make it unsuitable for many users.
Hopefully things improve in time, the problem is development is progressing at snails pace.