30 pin to usb, sending audio to my pc (Iphone 4s)

Ok here me out,

You can send audio from your iphone 4s using the 30 pin to usb to things like your car or Ipod docking stations. So why can't I send audio using the 30 pin to usb to my computer?

I don't want to use the 3.5mm adapter. I am stubborn. I have a generic 30 pin to usb charging cable. 30 pin sends audio through pins 2-3-4 (according to wiki) and usb well there's all sorts of mics that plug in via usb.

Is there some kind of magical mumbo jumbo that I don't understand thats physically stopping me from doing this?

TIA