There's something I don't understand, perhaps someone knows and can explain.

Why have the chosen to build it with only two wheels? It's clearly unstable and has to constantly adjust it's position and counterweight to stay balanced. Sure, it's super clever and I think it looks amazing. But surely it would have been far cheaper and easier to build it with three of four wheels so it naturally stable. It would have looked less cool, but I feel like that can't be the only reason.