because fantasy.

in a real world, you wouldn't have robots. too many moving parts. it is simply easier to make a huge ass flying gun.

not really. agile yes. stable not.

if you want to make the best design, make one that flies and has guns that shoot in all direction. a flying "ball" would technically be the best.

based on current energy sources you may say so.

but who knows in the future, we can draw power straight from the immediate air around us. by that time, energy might become so cheap that it becomes a no consideration issue.

and to say that aliens would have evolved into something similar to us is totally human arrogance and science of the 80s. Modern day scientists have since expanded the idea to include non carbon based life forms. For all you know, they could be moving slimey goo and that would technically be superior to a bipedal setup.

lel.