Chip n chase

I have never understood why rugby players chip and chase the ball. It appears to be the most futile of efforts and rarely comes off. A very low percentage of play considering that more often then not it has taken the attacking team a mighty effort to win the ball back ..... unless of course they intercepted a chip and chase.

The Gary Owen has a better success rate but why kick the ball away [other than to gain considerable territory] when possession is the name of the game? Can't score a try if you don't have the ball.