Any contest in the world needs an umpire. For the simple reason that you can’t box and count at the same time. You can’t be focused on the ball and realise when your opponent changes his players with a twin brother. You also need someone who can look at issues without personal investment.
This is the nature of human beings from the time we were children. Disputes were resolved by our parents and most importantly their decision was final. It is this submission to a referee that makes society work. It is what is called the rule of law. The law works because we submit to it and even its mistakes are final.