Evidence suggests that coaches and parents provide most of the stress for the kids.
When kids are stressed out they give up. They turn away or find some nonathletic avocation or become depressed. Adult egos often turn the game into a victory drive or a training ground for future stars, with their children as pawns. Many coaches decide that they want to show kids that sports can be a positive experience but that it can only be positive if they play on a winning team hence the coach plays the more advanced players most of the time, while the less talented kids play limited amounts from the coach s point of view the lesser kids share in their teammates on the field successes. Imagine how much fun it is to always having to congratulate his teammate for playing well from the bench.