[avaer]

A part of it is that the data models are genuinely different and different orgs want to do things in different ways.

Another part of it is that orgs recognize the value of stamping their brand on what they believe is a candidate for the next generation of the web.

But you don't need any of these frameworks to do WebVR; the API is (going to be) a standard and it's relatively straightforward to roll your own if you understand the browser's render loop and any 3D engine. I'm more worried by the fact that so much of today's WebVR code is just a layer on top of THREE.js. It's actually more of a monoculture than it appears on the surface.