Right now they're not practical to wear because people can knock you out and steal them from you. Plus they can't be gilded, meaning they're taking up an equipment slot that could be filled with a more useful cape. They're only worth wearing on alts that never step out of safe village grounds or left in your hearthfire as potential trade fodder.
Could they be made unstealable and wearable in a cosmetic slot? I hate the idea of losing my merch cape if the world accidentally gets nuked and I happen to be wearing it when it happens :/