I need to do a know of it.
Same reason yoyo is a thing I presume.
I don’t really play Kendama, but I found myself wondering this on and off for a long time and the explanations on the internet never really helped. I suggest that you find some videos to watch, go ahead and google Kendama. Personally, I like Haley Bishop. The Krom Girl Competition has a lot of amazing players with lots of talent.