I understand now why Allegri is attached to Sturaro so much.
So players do now that they are not worthy enough to be in a team and the only hope they have to play is making a personal good impression on the coach. If not as footballers on the pitch, as their eyes and ears in the look room. Someone who is focused at directly invested in supporting the coach and ensures that his grip is tight and mutiny arises and becomes threatening. The more such players a coach is having, working for him, the better he controls the team.
Players like Dybala and Higuain can easily be starters under any coach and can easily be starters in an equally strong, other team. But a player like Sturaro, would have no such option...