Great ball handlers have quick hands and are able to quickly transfer the ball from hand to hand with ease. They are also able to control the basketball at a high level. The windshield wiper between the legs dribbling drill is going to work on both of these skills, and will really help the ball handler improve their overall dribbling skills.
You may have done the basic windshield wiper drill before and are somewhat familiar with this drill, but this is an advanced version of the drill that is really going to challenge the player. It is also a ball handling drill that can be done pretty much anywhere that you have a flat hard surface. So it eliminates the excuse of not having a gym to go to.