Note: this isn't just a Bose thing. Bluetooth has separate profiles built in for phone calls/two way audio and one way audio. Because of bandwidth limitations,

Note: this isn't just a Bose thing. Bluetooth has separate profiles built in for phone calls/two way audio and one way audio. Because of bandwidth limitations, quality is essentially cut in half while using two way audio. While self-voice can add back some external noise, the bulk of the audio quality loss is built into the Bluetooth spec.