Why? To hide the stretch marks…
(ok, from a ca. 1978 joke about gay men. Come to think of it, I don’t know a gay man under 45 who wears one; I’m always tempted to remind those who do that the Carter administration is over :). Mustaches IMHO almost always look awful - at best they just hide part of your face. Sometimes, of course, that’s a good thing.)
I think a point is being missed. I have worked for several hotels that have EXACTLY the same standards and NO ONE wore a moustache. A friend of mine works for an accounting frim where they only allow moustaches. Still everyone there is clean shaved. At the hotel we all wore the same uniform. So why the need for individuality in the Police, Firefighters etc.