Not a dumb question, at all; it's a Great Question: why DEU, at all. We obviously need combat uniforms of many and varied sorts; and we need "work dress," too - again of a wide variety of sorts for "dirty" work (cleaning tanks in thaw wash racks after an exercise) and not so dirty work (sorting records on a computer terminal in an air-conditioned office). And I agree that we need a parade uniform and for the Army a patrol dress uniform, properly fitted, with the "right" headdress
would do just fine - blue for many corps and regiments, green for others, maybe even get rid of scarlets, entirely. So 3 orders of dress: operations, work and parade - dozens, of sub-sets to meet individual needs .. but no ties, ever!