I had a mustache on and off for years to look older as an actor. When I got old, I shaved it to look younger.
Like most of my shipmates in the Navy of the 1970s, I grew a beard because I could and other military services could not.
It also made me "feel" cool and allowed me to be less conspicuous off duty in Europe.
But it just never, EVER looked good enough for me. when I hit my 30th birthday, I forsook the beard, and went to the military extreme...going in for high-'n'-tight haircuts and a clean shave.
Occasionally, I'd grow the 'stache...
The Navy outlawed beards in the mid-1980s. I think they can still have moustaches.