If it were in the 'real world' the Health & Safety Police would make you wear both, as can happen in industry / construction. Its all to do with what the plug/muff will protect to.

On a personal level, I can stand the things. It is a fine line to tread between mandatory wearing of ear defenders and personal choice. We now have a note in the syndicate/ let day contract to that effect - its up to you, but we can supply them if you want.

Mind you, if some of the guns I've seen shoot were to wear hearing protection of any sort, they would miss everything!
Maybe Shoot Owners should wear them all the time, so they dont have to put up with the moans/excuses/grumbles from the guns or beaters!!