 Because you'll surprise yourself with something where you'll just have a go at it. Because think about all the different ways you can kick something up in the air. You've got the usual just forward kick where your leg goes out. You can use the side of your foot on one side. You can use the side of your foot on the other side. All these different ways that your leg can move. Those are all different ways you can keep the hacky sack up in the air.