That question did not have to be asked. In a debate, as you saw Kerry do, W can answer with whatever he wants to. He had so many occasions to get in whatever points he thought was necessary. He just didn't do it.
Baggy eyes Lehrer kept him so busy trying to defend himself, he couldn't think straight. Besides he had just been witness to a trajedy. I think he was probably suffering from sensory overload. Maybe a mistake on his advisors part but now they have time to learn from their mistakes.