Okay, I didn't know that. But this is still no reason
why ALSA shouldn't take care of mixing/scheduling/etc.
by itself plus providing low-latency performance
(with mixing) when that is required. Leaving out
mixing to third-parties, plus exposing a very
complicated low-level API and a complicated
plugin/configuration system (which probably
has taken a more time to develop than implementing
a proper mixing engine), has created lots of chaos.