The pitch caller has an excellent view of how the batter is responding to pitches ... which comes in handy when the scouting report is dry.
As for the ego issue ... I would think these same coaches that you complain about would believe the ego issue resides with the parents wanting their kid to call the game.
The kids do not have to call the game, but I do NOT want my DD to be coached by someone who does not accept input from his/her players. Especially when that coach was not a pitcher/catcher at the collegiate level, is not a qualified instructor, does not attend my DD's pitching lessons or spend any time on a bucket catching for her. There are a lot of great coaches out there, but there are also a lot of egotistical morons. My advice is parents do their homework before selecting a team, especially if their DD is a pitcher.