Well, I wouldn't be this outright negative - there are many specialized X applications that are unlikely to be made Wayland compatible in the near future (they are using xlib directly or a Wayland incompatible GUI toolkit, such as GTK2) or ever (dead usptream & complicated codebase), so it would be nice to be able to run them on Wayland somehow. The end result might not be as fast and elegant as running on Wayland natively, but something is better than nothing in this case.

Also Wayland does not yet have anything like X forwarding, which might be another usecase for having some support for X (I use X forwarding quite heavily on my desktop PCs for apps like Xchat, Thunderbird, Geany, etc.).