Lets designers build within VR. http://www.bit-tech.net/news/gaming/2016/12/16/unity-editorvr-preview/1
Sounds like the Unity team like the Unreal Engine VR Editor and are playing catch up. Nothing wrong with that of course. If/when VR/AR reaches mainstream most world building will take place within the context of the virtual. As will most of everything. I've read Ready Player One etc. I know what's coming. It's grim, it's depressing and it's amazingly cool. I can't wait to be able to live in a virtual world where 2016 never happened.
I disagree Guinevere, I think some final editing will be done in VR but the mainstay will be done in 2D, it's just easier to use a mouse for precise control and for getting a sense of things for a developer I think. If you look at classical 3D rendering and animation you'll also see designers use a 3 or 4 panel view during development of objects and their 3D view for checking and tweaking.