OpenGL ES 2.0 might be suitable for running a desktop framework, but it probably isn't suitable for the apps running on top of it. It's too cut to the bone e.g. it only supports triangles, lines and points as primitives, lacks geometry and tesselation shaders and has various other restrictions which might be necessary in a phone but should not be when running against a PC GPU.
Guess what? That's what the graphics cards do. No consumer graphics card does quads, strips, fans, big dots or wide lines in hardware. The driver has to re-work them on the fly.
OpenGL ES also needs a separate, standard library for doing immediate mode rendering, matrix math, etc. Newbies can't be expected to do all that stuff for themselves. Direct3D has Direct3DX, OpenGL ES has nothing (I suspect this is one more reason why they're trying to keep OpenGL ES off the desktop when what they should really be doing is creating that library and getting people to use it...)