Standing on two feet gives an impression of a self-supporting body. Having a support at the back would give the impression that the body is transported by a fo

Standing on two feet gives an impression of a self-supporting body. Having a support at the back would give the impression that the body is transported by a forklift. It's irrational, but we know how the irrational deeply affects human relations. Think how accepted are those "telepresence robots" that go around campuses looking like a TV set hooked up to a vacuum cleaner (hint: they're creepy). You don't want to make the same impression.