It is not allowed in 2.2 because we are trying to emulate 1:1 competition at it's highest level. DIG is allowed in 1:1 competition. 4WS offers benefits that far out way that of a simple DIG unit. Being able to independently steer the rear axle allows much more control and makes course design all the harder. Instead on rowing upstream on the matter, why not do some research and find out why the rules are the way they are.