Probably because it has to extract the audio, send it to the bluetooth audio chip, from there it probably gets processed again, then it stands in a bloody line to waiting to get blasted one little 0 or 1 at a time through the bluetooth radio, magically finds it's way to your headsets radio, gets magically reassembled (btw if one of those 0 or 1's is missing a search party is called in), by a much slower chip I might add, from there converted into a analog signal sent to the drivers in the headset, then into your ears and then your brain has to process it.