> Wow, I don't think so.  Telephony is seldom concerned with the content
> of audio streams, and indeed one generally wants to keep them out of
> main memory if at all possible (in software VoIP applications, it's
> seldom possible, but that does not mean that one does not _want_ to
> avoid hauling it into memory and working on it there...).

I bow to your experience in this area, but in this case the hardware
devices basicially *are* sound cards, are they not? They're just sound
cards with a different interface to the outside world, and a few extra
bells and whistles (detect or change off-hook state, detect or generate
ring voltage, etc), and in some cases, fancier codecs... 

You may not *want* reading and writing audio streams to be your
interface, but if that's the fundamental interface offered, any other
kind of interface must necessarily be built on top of that...  right?
And given that we have an interface already for audio I/O, it seemed
logical to leverage that...