Because there is too many people that only see 22 people running behind a ball, but it is not that simple, that is why they have a DT, this person is very important, he is like a chess player that put his best 11 pieces in the field with a strategy in mind to beat the opponent. This is the reason why exist a lot of formations and positions in the game. All the team games have a strategy and it is very important to play a game. It is like chess but with moving pieces.