Because it's not using the relevant framework at all, it's gone and reinvented the wheel without a pressing reason to do so and this will be very likely to create problems if the part is at all successful.
Its more a case of predating the wheel as far as I can tell. In terms of frameworks I don't think it matters as of itself - but once that means you have to write two different versions of the same codec chip driver for example yes it matters.
This is all driver specific stuff, there's nothing that needs doing here immediately outside of the driver that I can spot right now.
Well our agenda right now is to strip out the crap, polish up the various bugs found in review (and in staging its already getting a trickle of very useful community input swatting silly error path bugs, signed/unsigned typing etc) and then assign someone in Intel OTC (hopefully if things go to plan someone with prior ALSA dev experience) to make it a good ALSA citizen which probably means using ASOC or similar.
Putting it in staging allows that work to be done in public in a meaningful way where the code and changes get review.
Alan