Eventually, Moses comes to the realization that the Lord has been teaching him a basic lesson about human behavior. Great miracles, no matter how awesome and overwhelming, do not change human behavior and beliefs in any meaningful fashion. Pharaoh will be defeated only by force that strikes home to him personally -- his first born child is killed and he is also in danger of being killed. It is not the miracle of the first-born killings that impresses him. It is the fear for his own safety that the miracle engendered that causes him to free the Jews, a decision that he almost immediately regrets. Miracles may raise Jewish faith temporarily but they do not form the methodology for developing lasting faith and commitment.
After all of the miracles, the Jews are still capable of making and worshipping a golden calf and rebelling against the rule of Moses and G-d. Moses realizes that no matter how many miracles occur, faith has to be nurtured and developed and maintained from the inside and not from outside circumstances and happenings.