Whats the point in kicking it away?

any one who watches a south african game will see how much kicking fourie du preez does from a scrum/ruck.eg, pierre spies gets the ball-gets tackled,south africans protect the ball-du preez comes and box kicks it back to them with SA wingers chasing, the opposition catch it, kick it back further and SA have lost a whole lot of groung-why dont they just run it