Now you can set your tactics globally for a whole game.
But at times you want your players to react in a certain way on a certain situation.
You can set short passing for a keeper (so he won't just kick the ball in field). But you can't set what your defenders should do in that situation.
Some teams push the backs in midfield, the center backs go wide etc.
Other teams let a playmaker drop back to ask the ball and start the game.
Obviously the majority of the game the players make the decisions based on your global tactical instructions. But sometimes manager want to have fixed pattern: say how players should react in common situation. This would be nice.