I cant understand why anyone would turn the volume down on their radio so they cant hear it, you can talk over a radio transmission on an aircraft intercom, aslong as you listen out to the callsign at the beginning.
However, i often find that listening to others can give you information on the position of other vfr traffic, that you havent been alerted to, because the atc is busy. You would miss out on this if you turned your radio down, so why do it?
NB