Remoak, listening on 121.5 on approach is very important - it might be the only way that ATC can call you if you screw up a frequency change, or suffer an undetected radio failure. My favourite radio call on 121.5 while on approach/departure was the warnings by the USS Vincennes before they shot down the Iranian Airbus. Now that is one call you wouldn't want to miss!
Also, I've seen as a result of this policy crew forgetting to listen out on 121.5 at all during a flight, as they don't select it on departure and forget to set it up at top of climb.