The writing part isn't really the main benefit of whiteboarding. Standing there, pointing at things and chatting about it is a really big part. Then there's the physical size. Quite often I find it much nicer to stand in front of a board and draw on a large scale. The current attempts at remote whiteboards are really not suitable replacements.

VR would a giant help as body language, gesturing and physical size all become much easier to see. Of course, that would require quite a leap forward in VR to accomplish that level of avatar.