Being able to handle the basketball comfortably with either hand adds a lot of value to a player, especially if they are a primary ball handler. This drill is going to force the player to work on both hands by having them dribble two basketballs at the same time. It eliminates the players ability to switch the basketball over to their strong hand when they get in trouble, which a lot of players have the tendency to do.
This is also a great drill because it is a competition between each group of players. Both players are pushing each other to get better and to get out of their comfort zone. Anytime you can add a competition aspect to a basketball drill it really helps to promote skill development.