"So following that logic, why not bin the dress regs completely then? Only wear uniforms when on parades or when in fighting mode, so just wear civvies; have your hair as long as or in whatever fashion you like; have as many earrings and tatts as you like? So I can grow a full set of face fuzz but can't grow sideburns to the bottom of my ears?"
yes well -your opponents probably dress that way - certainly in many recent conflicts - and it doesn't seem to affect their ability to fight.
A smart uniform really went out at the end of the 19th Century - once camouflage came in. The rest is really dressing up on high days and holy days.