I think an argument is it's better to be completely different than close but not close enough. As in uncanny valley. If it can't actually be a perfect human ar

I think an argument is it's better to be completely different than close but not close enough. As in uncanny valley. If it can't actually be a perfect human arm, it's better to have a clearly not-even-trying robot arm. It probably has several different roots. Two at least are: One is the uncanny valley, which has to do with fitness for reproduction and avoiding disease etc. I'm talking at the animal brain level. Any animal will avoid a deformed version of itself. A human will be revolted by another human who's appearance is barely any different from their own, seen from an outside perspective like an alien, but they will love a dog to pieces, even though the dog looks infinitely more different than the human with a slightly too big forehead or something. Another element I think is probably based on deception. If you can do a perfect fake, then ok, but if it's only close, then at both subconscious and conscious levels you don't like being deceived, because that is manipulation, someone else taking control that you didn't voluntarily give them. A steel pipe arm does not deceive, or more importantly does not attempt to deceive anyone. It ends up being as emotionlly neutral as the same person holding any other tool. Instead of holding a hammer with their hand, they are holding an arm with their shoulder.