Why are you yelling?

This week I was reffing high school games and I really got a chance to observe coaches and noticed a interesting trend. Most coaches yell a lot. But that's not news to anyone but when I listened to what they were yelling about I noticed that they didn't say much. There was a lot of COME ON! , WHAT ARE YOU THINKING?, HUSTLE, WAKE UP JIMMY. How are any of those interjections help? I'm sure I've been guilty of doing it myself, but I'm going to change my ways. If I have to yell, I will yell out specific instructions like BOX OUT, GET BACK ON DEFENSE, MAKE THE EXTRA PASS. Because the coaches who emphasized more of their yelling on instructions seem to win more games than the one who don't. That's what I got out of my unofficial scientific research.