[Thad House]

One of the best ways to improve stability of any object is to move the contact patches as far to the outside as possible. On a robot, this involves moving the wheels as far out as possible. Because on a WCD the wheels are cantilevered, there is no need for an outer frame rail. Because of this, the wheels can be as close to the edge of the allowed perimeter. This allows for a stabler robot.
Another advantage is because the wheels are on the outside of any frame, and usually on live axles, remove a wheel only requires removing 1 clip or screw, and the entire wheel pulls off the side. This allows a wheel to be changed very quickly, usually without having to adjust chain tension, or remove alot of robot parts to get to it.