If the ball is on the far left side of the field and a runner is starting toward the middle of the field with a defender in front of him, if the space is available, it's in his best interests to make a looping run.
If the runner makes a straight run, it's easy for the defender to see the ball and the runner.
However, if the runner loops (or bends) his run, the defender will be forced to turn to see him and thus lose site of the ball.
The alternative to the defender losing site of the ball is they will lose site of the runner.
Either way, it puts the defender into a precarious situation as a good defender will try to always see the ball and the player they are marking.
The wider the looping run, the more difficult it is for the defender to bend the run out wide and see how many goal scoring situations you can get into.