Having good relationships especially between pitchers and catchers helps the overall team chemistry as others pointed out.
While it does help player growth for catchers to learn how to call pitches as well as control a game and set defenses as they move up in level of play they don't do it as much as some may think.
Once the ladies hit 14U we would look at the schedules and see where we could grow the ladies or, depending on how the game goes take advantage of opportunities to get them some time calling the game but it was never a plan to have the catchers control the game. Once they went on to adult ball 18+ yeah it was their game 100%. The dads would just get them in events, keep score coach a base and let them play.
With that said, most of your upper programs Travel, HS, College rely on staff to help manage and control a game. You need pitchers and catchers that are team players and understand how to play the game smarter and faster and utilize all resources.
Naturally there is more to the game at the upper levels of play than just calling pitches on where the batter sets up or hitting style.
Todays top programs look at situations, tendencies, previous AB for setting defense for specific outs etc. when calling pitches.
10 years ago one would hardly see wristband signal systems...Now just about every top level team utilizes some type of signal system to call pitches, set defenses and alert the fielders of where they are trying to get the hitter to place the ball in or, for potential out opportunities when there are runners at first and or, third.