Now for some rampant speculation why. Maybe working with the phone was reserved for officers at the higher end of the ladder of success, most of them are also older. The fellow standing looks more like a beat cop, perhaps there to get orders or carry messages, while the men sitting and one on the phone are older and larger and maybe senior officers who make more money and have more status. Wonder what the stripes on the sleeves mean? Typically in military and quasi-military organizations they mean more status and rank.

All speculation of course. Maybe all these guys had thyroid problems and were on medical assignment to the phone desk.