What is the purpose of the bowling ball being made of plastic?

Answer 1

A plastic coverstock on a Bowling ball helps when you need to convert particular spares, or when the lanes get incredibly dry. Since the plastic coverstock on plastic bowling balls is hard and non-porous, on most lane conditions, it's not going to hook very much. An example spare to be picked up is the 10-pin (for righties). Using a reactive resin bowling ball isn't always the best idea. If you hook the reactive resin bowling ball at the 10, odds are that you're probably going to throw it into the gutter because of the angle you're creating, or the ball it going to hook right past the 10. With plastic, no matter how many revolutions you put on the ball, most of the time the plastic ball isn't going to hook, so you can throw directly at the 10 with 600RPM and the ball won't hook all that much away from the 10 (on dry lanes, it's a completely different story).