Well, the greater part of the reason may be that - as you clearly understand - this function is almost always associated with passing the audio via Bluetooth and while there is an "Audio" forum here which i confess, I have just about never looked at, it is generally accepted that Arduinox are not suitable for any serious audio communication purposes.
(Why? Because microcontrollers in general are not appropriate for real-time audio. PCs long ago devolved audio processing to purpose-built peripherals.)