If player A is on the bench...they cannot be on the court.
If player A is on the court he can either keep playing or he can foul and come out.
One of these scenarios is the only way to maximize a players minutes. You can't maximize a players minutes by sitting them on the bench. It's the same reason I don't like sitting better players to start each half. You just guarantee that you will limit their potential minutes.
People say who starts doesn't matter. Baloney! It does for a couple of reasons. Maximizing the potential minutes of best players AND getting off to solid starts. You will always have the choice who is in at the end of the game.