I didn't before, but now it exists I want one. And I have (mostly) working legs.

Though I do wonder if it would be more stable with more legs (6 perhaps), as natural crabs have, as a four leg design will result in a lot of time when the centre of mass is in an inconvenient place with respect to the three legs currently on the ground (I'm assuming it moves slowly enough that it is rare more than one leg is raised). Unless the technicalities of more legs would make it worse in ways less convenient than the balance bonus.