There are always slightly harder, and better ways of doing something which the accelerators are better at. Audio acceleration I guess peaked too early or they just couldn't get the tech demos as impressive as graphics.

I remember reading about a demo, which I believe was from Matrox. They managed to get an audio 3D environment working over a pair of stereo headphones which was good enough that you could play Doom headless. Just close your eyes and you could tell where people were.

A lot of what I read about here is that prerecorded samples is good enough, in the same way that raster lighting is good enough and raytracing is a waste of time.