You only get limited(I think 10 ) playbooks. If you run the Pro Set(for example) you might have 4 or 5 different playbooks just for that formation. For ex. Heavy Run, Heavy Pass, Balanced, Fall Behind Desperation, Conservative Passing instead of Run to Run out clock when winning, and anything else you can think of.
Ok , now you just picked up a team that run Trips formation. Now you need another 4 or 5 custom playbooks. What do you do if you have 3 teams each with dif formation ?
Well, one solution is to run them with dif id's.