A player that is able to handle the basketball moving up and down the court without having to look down or worry about their dribble is going to make a big difference in running the offense, compared to a player that is constantly worried about losing the ball and is always looking down. The goal of this two ball dribbling drill is to help the player learn to dribble with their eyes up, handle a basketball with either hand, and also do a little conditioning.
To make this drill work though the player really needs to push themselves and challenge themselves to go their absolute hardest. This is where the most growth is going to happen. So during basketball training make sure that everyone is working their hardest and isn't afraid to mess up.