Another thing to keep in mind about the rules of baseball is who is pitching. In most situations, the pitcher is the person who is throwing the ball. He is on the other team as is up to bat, or hitting the ball. This is the way the game is played in most forms, and it is the best way to play because it allows the infield, or defense, to play as a team. So, why would it be any different?
For those who are just learning the game, it may be a better option to have someone that is either an official or non team member or coach to play the pitching role. For new players, it is important to teach them how to swing and how to hit the ball that is coming in at them properly. You do not want these young people to try to hit balls that are not well thrown. Therefore, in t-ball and games for beginning players, having a coach or even a non member do the pitching is best.