Eh. That's kind of like complaining that a human cheats by eating plants and animals. If you really wanted to show an example of something walking, it should

Eh. That's kind of like complaining that a human cheats by eating plants and animals. If you really wanted to show an example of something walking, it should have a nuclear power source, or have photo cells to absorb sunlight... But yes, I get your point. It'd be nice if they ALSO showed it carrying its own power source. I believe that would just lead us to questions of "how far can it go with a given power source, at a given rate?"