It seems fairly common in Generals, and maybe more common in Army Generals, especially in dress uniform. I seem to recall that it was kind of optional in the Air Force. Generals are surrounded by staff. Everyone that matters knows who they are, and they will usually be presented by name before they speak. They’re kind of insular, and a little bit crazy because of it. I remember people scrambling around ahead of General Creech to put the red dictionaries in drawers because he hated the color red.
Or maybe it was because it was top generals.
Notice, however, that General Milley is not wearing a tag at the Pentagon when giving a briefing, though he wears it at official gatherings..
-PJ