A good playbook can help you teach great tactics to a well-coached team, so that you win more often. 

Remember, you coach athletes, not plays. Your plays, and your playbook, are not silver bullets. They open up a variety of tactics your team may choose from in the heat of a game. When nobody has the time to create more viable options, practiced plays come into play. 

The playbook serves the purpose of preparation. The plays in it serve the purpose of defining terms you would use during a game (and game-like practices).