So, if it was just the GPUs, that wouldn't be too strange, all three major vendors claim (at least in public) to have secret sauce that sets them apart and a class driver would reveal that to be largely hogwash.
But in the other groups I'm left with a lot of questions - why for example network chipsets but not storage controllers? Why webcams (hardly the most trivial devices) ended up UVC compliant almost down to the very cheapest products on the market while DVB remains an endless series of incompatible chipsets doing much the same things but all in very slightly incompatible ways?
And why the timing? Was AHCI somehow perfectly timed for an opportunity to standardise storage controllers? Is there some clear reason such a standard couldn't have emerged a year earlier? A decade earlier?
USB mass storage shows that you can crank out a standards document even if the contributors can't agree on anything of consequence. Six different ways to do either of two different things, but only six, and not sixty or six thousand. And it also shows that having done that the market explodes.