Hair length sort of got entangled with political views during the 1960s. Also if you wore a beard back then you were assumed to be a liberal. So that had an effect on the military that has lasted until this day in their attitudes towards hair length even though it now means nothing in civilian life.
My husband just recently retired from the military....for all these long years, he has had short, short hair...yet before he went into the military, he had what I would call medium length hair...I am now curious, now that he is a civilian again, if he keeps his short, short haircut, or if he will let it grow a little longer again....I do know he is contemplating growing his moustache longer and adding a beard...
If he does grow his hair longer, grow a longer moustache, and adds a beard, I may have a whole new husband...