Leather Armor? (NO HOLDS BARRED!!)

[Tarbicus]

How is that different to stipulating that this armour is ceremonial and has no function other than to look pretty - to serve one's vanity.

Because it's not intended for ceremonial use, it's intended for general and battle use. If a musculata was part of how a high ranking officer was distinguishable on the battlefield, just as skins for velites, etc, then it had a battlefield purpose.

As Travis points out, morale is hugely important, and if part of that projection of one's image is in any way inspirational to the men (or the wearer) then so be it. It may seem a foolhardy thing to do, but there are accounts in war of leaders who apparently have little regard for their own safety and expose themselves to the greatest of danger seemingly unnecessarily. With some it is just plain dumbness, but with others it seemed that they were almost blessed with divine protection (Caesar wasn't averse to it in antiquity, just as Lt. Spears of Easy Company in WW2 wasn't). Perhaps these Romans felt that way, or wanted to project that image, whilst wearing no armour at all was unacceptable or made them look like low rankers?