I've wondered this also. I'm not sure whether I believe it to be the laziness or the fact that they want to portray the humanity inside them. However, seeing a ribcage fully intact for Sektor and Cyrax when they both have chest cavities that produce missiles, grenades, and electrified nets is beyond me. Also, Cyrax completely disassembles himself in his teleport move. It would be nice to see them rendered internally as cyborgs, but I doubt that will change before launch. The same arguments can be made for how the opponent is still moving after Kitana shoves her blades through the back AND front of their face and how the technology shows soft tissue such as intestines and organs cracking just like the bones do. BUT overall it still looks pretty neat IMO. So I guess, just like the plastered "There's Something About Mary" hair that everyone has, we'll just have to overlook for the sake of it.