I’m sad to see the resistance to support WebGL among Microsoft and Apple. “Security risk” is just a scapegoat. Sure screen scraping is a valid concern but there are ways to prevent it for sure, for example forcing memory reset, disabling app-level texture reading, frame buffer read-back, etc. And Microsoft’s ActiveX is not a bit better in that regard, probably much much worse.
The real reasons are most likely business reasons: Microsoft doesn’t want gaming to move to browsers, and neither does Apple. Microsoft has dominant position in desktop gaming, and Apple dominates mobile app sales. So why would they embrace multi-platform 3D in a browser? It doesn’t make (at least at the moment) business sense for them. Sad.