More easily said than done.
Wxwidgets is itself already a wrapper over the underlying C APIs provided by the OSes. This makes sense if the target language is C++. But it is a real maintanace nightmare if the target is a "managed" language. Then it must be de-wrapped as a C api and every time there is a change in WxWidget it's probable that the C-inteface must be updated as well. Having a straiforward C implementation reduces much of this maintanance overhead.