To coach Xs and Os is good, but to coach attitude is better. You have to know all the nuances of the sport -- you have to be able to design plays and teach technique -- but the coach who leaves off at that will never be a great coach.
Great coaches get the best out of their players. They instill in them confidence and enthusiasm. They inspire. They imbue in their players determination and effort. To leave off coaching at Xs and Os is to leave off coaching before the real coaching has even begun.