I'm not sure how a Coach's Ego would come into play here. Pitchers need to learn how to pitch by paying attention as the game goes. Do coaches need to let kids steal, hit and run, and bunt whenever they choose? Your MLB example are of pitchers who HAVE learned how to pitch, and have people behind them to adjust to situations and different hitters. Most high school teams don't have kids on the same page as MLB players. They are there because they see the little things, communicate from pitch to pitch and hitter to hitter. They've learned to look for these things from coaches positioning them and experience.