The coaches have more information available to them than us. The thought is that they are more informed about the team because they actually attend the practices and talk to the players. (I know crazy) They use that information to make their decisions about who is going to play and what plays to run. No one is saying they are never wrong, but they do know more than you. Unfortunately, game planning is a little more complicated than run the ball and pass the ball.
Here is a hypothetical scenario, the coaches watch Warren fumble several times in practice this week, miss key blocks, and generally look bad. They use this information to decide he should not get much playing time because they don't trust him. Fans get really upset when he isn't used and has no idea why they didn't play him and blame the coaches for not using the obvious all world RB they have. Like I said this is hypothetical but these are the types of things coaches use to make decisions. Does this make the coach wrong? Hermann has repeatedly said you are only as good as your last practice. I don't know the reasons anymore than anyone else but sometimes you just have to trust the coaches. Let them game plan how they want and wait to see if there is any improvement.
