People don't care about audio in the way they care about graphics.

Oh, to be able to go back to 1998 and give Aureal better lawyers...

hardware accelerated audio: neither particularly critical nor is the relevant hardware commonly available on end-user systems

But that's a circular argument. Hardware accelerated graphics weren't necessary for most of the 1990s, and we enjoyed the games then. But we realised it would be cool to have more powerful graphics. More demanding software inspires more powerful hardware, which permits even more demanding software, and so on.

There are several ways in which we could be making good use of hardware accelerated audio, and I listed several in this post. But until we see developers and researchers start attempt these things, and make it clear to hardware manufacturers that they want more power, then we won't see much movement.

I think the main reason why there is no huge demand for audio hardware is that it's perfectly possible to do render 20-30 three-dimensional sources in realtime in software, in CD quality (and, without totally killing the CPU). The difference between 20 sources, 200 sources, and 2000 sources is very small, if audible at all. Therefore it is conceivable to get away with fewer.

Monitor speakers and headsets are often of embarrassingly low quality too, so even if the sound isn't the best possible quality, a lot of people won't notice at all (and they'll not notice the difference between the most expensive soundcard and the onchip one, either).

It is, on the other hand, not trivially possible to do a similar thing with 3D graphics (not at present-day resolutions, and not with state-of-the-art quality, anyway). The difference between 20, 200, and 2000 objects on screen is immediately obvious. Displays are usually quite good, so the difference between good graphics and bad graphics is immediately obvious, too.

That doesn't mean that OpenAL is not being developed at all, however. The OpenAL-Soft implemention, which is kind of a de-facto standard (as compared to the dinosaur reference implementation) undergoes regular updates and implements several useful self-made extensions.

I'm not convinced that the number of objects was a big factor. For the first 5 years of consumer graphics card availability, pretty much every game that could use a GPU needed a software fallback. You had to be able to show the same number of objects whether you used hardware or software, just at a different degree of quality. The same would apply for sound now. (And by quality in the audio context I don't mean using 96KHz / 24bit sound, I mean simulating reverb, occlusion, etc - things you can't do very cheaply but which you can discern on even the cheapest headphones.)

Oh, to be able to go back to 1998 and give Aureal better lawyers...

I just read up on that court case. Wow, just... wow.