There are not enough real coaches spending their time to coach young players, and for that reason, parents have to do the coach job.
To direct a group of kids to play baseball doesn't meant to be a "coach". Must of them don't know a lot about baseball and from the small group that have some knowledge, the most don't know how to teach. Been a coach is a lot more than make a line-up, do some practices, and let kids to play, if you don't know "what" and "how" to teach baseball, it is a very difficult thing to do.