Uniformity in dress leads to uniformity in thought. For regular, conventional units, this is a trait line units strive to achieve. In a high intensity fight, it might be a good skill.

Unfortunately, regular wars are hard to come by. In messy, politically complex wars, like Vietnam, Afghanistan, Iraq, Somalia, uniformity is a bad thing. Fortunately, special forces guys realize how little uniformity matters. (Regular line units learn it to, at least the guys fighting the war. Most CSM at BDE and higher will never learn it.)

(On a note sure to start a fight, only the US Army can be in a war and short soldiers and exclude them for silly reasons. For example, excluding Sikhs for head gear and oh, excluding Arabic interpreters for sexual preference.)