Interesting concept, but it looks like it wobbles around quite a lot in "wheel-mode"; and this is at the very low speeds shown in the video. I think it's reason

Interesting concept, but it looks like it wobbles around quite a lot in "wheel-mode"; and this is at the very low speeds shown in the video. I think it's reasonable to assume that it would be almost uncontrollable at higher speeds (leading to damage to itself and other components over time). As others have already mentioned, maintenance would be much more complex too with so many moving parts, all of which could potentially be damaged; and it certainly would be more expensive than a simple wheel.