Not sure where this craze has come from but only heard it today as my little girl was watching some YouTube today to then my wife replied that these are all of a sudden quite the rage for kids, even though they were created to help kids with sensory needs. Ironically, the wife received an email from the mainstream primary school to advise that they are to help special needs children so please don't bring them to school.
I wouldn't normally see the fascination in these but because I can relate to how my autistic son loves things that spin I could see how he would get a kick out of these things. Other than that though, the buck stops there. If you're playing with these for any other reason that's just bloody strange to me.