It is important to be able to handle the basketball with either hand comfortably. You don't want the defense to be able to force you to your off hand, and then you not be able to take advantage of it. Unfortunately though, a lot of times players avoid their weaknesses instead of focusing on them and developing them.
That is why two ball dribbling drills are so great. Because there are two basketballs, the player has no choice but to work on their weak hand. This is a more advanced dribbling drill that is going to really help to develop good handles and over all hand eye coordination.