Dribbling low to the ground helps you with 3 things:
1. Protection: the ball has less distance to travel from your hand to the ground when you are dribbling low. With that being said, the ball spends more time in your hand and less time out in space. When the ball is in your hand, it is protected!
2. Quickness: playing low allows you to never wait on the basketball to be back in your hands to make your next sprint step. Also, dribbling low allows you to be in a more athletic stance which gives you quicker reaction time and puts you in a better position for quick movements / sprint steps.
3. Accuracy: dribbling tall and trying to make moves is difficult - you have to pass the ball further and higher around your body while trying to avoid your legs and hips. The margin for error is small when you're playing tall (that rhymed).