No, it's evolution. Mammals burn a ridiculous amount of energy just existing, so evolutionary pressures tend toward more efficient muscles and body geometry.

Electrochemical reactions in your muscles combined with the mechanical advantage from the geometry of your joints and ligaments is simply more energy efficient than most mechanical or electromechanical systems. On top of that, our learned and evolved kinematic algorithms result in vastly more efficient control. Humans tend to be pretty good at using only exactly as much energy as required for a given action. Overshoot is quite limited compared to robots.

Your suggested actions seem inefficient, but if you look at the actual energy expenditure, mechanical means are much worse simply because mammalian muscle is so efficient.

There's a difference between consistency and efficiency.

I read efficiency as "Energy inputted to accomplish a task", in which case, biological systems are far more efficient than current-day mechanical ones. It's a tradeoff.