Typical for the South American coaches. They don't play the young talents that play in Europe. It was the same story with Messi a few years ago in this tournament. He was Argentina's best player, but started the first match on the bench. Finally, he played all rest matches and became the best player of the tournament.
Rafinha's qualities are way better than all the other players in their U20 squad. It will take some time to open the eyes of the Brazilian coach.