Guess what, there's more to military life than standing at attention, marching, and shouting "YES SIR!" Military personnel can be as laid back and "unprofessional" as anyone in civilian life. Not too long ago there was that story in the news about the US Navy pilots who drew a giant penis in the sky, which definitely would not be out of place in the Planetary Union's Fleet. The military isn't a cult that transforms people into ultra rigid and formal, those who serve are just ordinary people with a stressful job, and they blow off their steam the same way anyone else would. And what we see on Orville is consistent with that mentality.