The thumb is typically what people use to start off the golf swing. They grip the club with their index and middle fingers on one side, and then wrap their thumb underneath it. This has two purposes; first, it helps them apply pressure to keep control of the club throughout the swing, secondly, it allows them to "feel" for any tension or movement in the ball before they take a shot. This means that if your glove is torn at all on this spot (the wrist) during play time it can lead you straight into pulling up short without fully releasing your grip on the club.