This is standard procedure during anything out-of-the ordinary. You and I know the difference between a missed approach and something that's actually a big deal. Other pax don't and some might become concerned over nothing.
Also, if there was a mechanical issue with the aircraft, the pilot was probably talking it over with folks on the ground. The last thing some jittery flyer needs to hear in the headphones is his/her pilot talking about the malfunctioning flaps on the bird. Again - very interesting to you and I, but cause for alarm for those not necessarily in the know about the workings of airplanes.
Does anyone else think Ch 9 should default to "Rhapsody" when switched off?