The same reason most of AMD's 'open' initiatives don't gain traction: they throw it out there and hope things will magically work out and that a/the community will embrace it as the standard. It takes more work than that. What AMD historically hasn't done is the real grunge work of addressing the limitations of their products/APIs and continuing to invest in them long term. See how the OpenCL (written by AMD) Cycles renderer for Blender worked out, for example.

Something AMD doesn't seem to understand/accept is that since they are consistently lagging nVidia on both the hardware and software front, nVidia can get away with some things AMD can't. Everyone hates nVidia for it, but unless/until AMD wises up they're going to keep losing.