I’d imagine something like this would be useful in a live setting, where you can listen to the Beatbuddy in headphones (say, to listen to a metronome click to ensure your loop is on tempo), without it coming through the speakers. That is, until you unplug the headphones, or use another way to fade the speaker output audio back into your mix.
I was surprised that reducing the volume with the main knob also meant quieting the headphone volume, even with its own dedicated wheel. I thought BB might digitally recognize when headphones are plugged in to enable independent gain adjustments–maybe this could be added to the next firmware update?