For me, it is really aesthetic. Not all unofficial flair will make an ugly/cluttered/ridiculous uniform; but UP approved uniform, in full compliance with the guide to awards and insignia, will almost never look too bad.
I don't have much artistic or design ability, so I stick to a simpler uniform. I don't even like temporary patches much because they are either a pain to sew on and off or they are dangling things that can get caught on stuff. Same reason I don't like the powderhorn or emergency preparedness insignia- more stuff to catch, clang, remove before washing, and put back on a