Genuine question: where does the obstacle lie here? The BCM2835 is a hardware video accelerator with a small ARM on the side. GPU libraries are available. Is it something missing from X or Firefox?
tldr: full minute to boot X and chromium just to implement simple 20 lines of python application.
Of course you can build an OpenGL ES application on the Pi – there are people doing this. But that's a absolute frigging world away from being able to build a usable UI on it.
For example, I am building a device that interacts with a user. It basically looks like a standard iOS or Android app, in that it has a few screens of text, some form fields, select boxes, and other UI widgets. Building this sort of application as a barebones OpenGL implementation would be stupid.
Using the web with embed system allow new horizons and new people play with this. Of course, we can do applications with OpenGL but the first step can be with a universal environment like a web.
In the end I have been using a Go web server with websockets to display a single-page app in Firefox running under X. It's still not totally satisfactory though – UI is slow due to the lack of HW acceleration, and there is no nice solution for on-screen keyboards, so I'll probably have to implement one in JS eventually. Touch screen support is sketchy at best.
Are there other similar platforms out there that might offer HW acceleration or working Android implementations? I also had a crack at the Orange Pi which claims to have functioning Android, but… let's say that's an overstatement.