Because they train the body to work as a complete unit by training movements not muscles. As a result, resistance band training improves acceleration in coordinated movements related to the specific sport motion.
Whatever your current form is, use theProPullto work on your acceleration from the reach back through release and you will get 7-8 more feet of distance than you have now, for every 1 MPH of increased disc speed.
To get better ... ProPull, FIELD WORK, PLAY - REPEAT .. REPEAT...