That one call can make the difference between triumph and defeat. Players have to know that the person making that call has a knowledge of the game second to none. Certification is what tells them you are an authority of the game to be trusted and respected. It is the key step for anyone looking to be an official in the sport.
For current officials, re-certification ensures that you are up-to-date with the game and still able to make those crucial calls that can decide a match.