While this skill is often used for fun, it also has practical purposes, especially when the skill is upgraded to the maximum.
Balls usually aren't extremely useful, spawning 6 at a time can quickly allow you to fill up a gap. This is useful if the gap is closed (possibly by transparent planks or boxes), and the balls are spawned inside the gap so they cannot escape.
Balls can also be used in survivor for many purposes. If a mouse is wall jumping and you don't use hotkeys, you can summon a ball on top of their head so they won't be able to wall jump. With the "multiple balls" perk, you can summon more making it sure that they can not wall jump.