I've heard it many times: "My son quit playing baseball because it wasn't fun anymore."
Most of the times that I hear it, the reasons are one of these:
Coach turned the kid off the game.
Kid was experiencing too much failure.
Kid was feeling too much pressure to compete and do well.
Kid didn't want to make the sacrifices needed to play or didn't want to put in the hours and work associated to playing.
Kid didn't make the team that they wanted/felt that they deserved.
What other things make baseball not be fun anymore?