He is also not very good at catching passes which is why I am going out on a limb and saying he hasn't been as involved in the passing game as I and apparently you also would like him to be.
Also, while he can catch the ball out of the backfield he does not excel at it and in many ways that limits what we can do offensively when he is on the field. If he were better in those 2 areas then we could be more clever in the formations and plays we run because the defense would not know what is coming. Right now if it is a passing play, he is often taken out of the game. If he is in, there is a high possibility that it will be a run.
When we had Chester Taylor he was not as good as a pure runner but he was much better in pass protection and in catching passes and it made the team more balanced. When AP moves on if we can find another CT type player we may see a much better overall team, although it will almost certainly not be as good running the ball.