Who needs efficiency when we're talking about giant freaking robots? The whole point of giant freaking robots is giant freaking robots being giant freaking robots.
We live in an era where this can even be a thing. Casually. For no more reason than "it looked cool in the animus and games." I don't care if they fight like 90 year old crippled blind Batman impersonators! At best I get something awesome! At worst I get to see a humorous cultural exchange between two societies which have been fascinatedwithgiantfreakingrobots.
They're like giant mechanical people made out of weapons and armour. It's super impractical and nonetheless extraordinarily awesome. You know, like magic, except we can actually make giant robots.