Probably that they aren't really useful in a long-term sense. They can't be used for transporting much, can't be used easily when sick, won't be able to transpo

Probably that they aren't really useful in a long-term sense. They can't be used for transporting much, can't be used easily when sick, won't be able to transport young children, and become useless in cold/hot/rainy/and snowy weather. Same moat as any other fad that targets the single young urban knowledge worker; their needs will eventually grow beyond it. I mean, skateboards do what these do as well.