They do have a lot of utility. Particularly for the first generation of kids in the US to have a lower percentage of drivers licenses and car ownership than a generation that preceded it (in the automobile age, obviously).
As a cyclist, I'm amused that people choose this more dangerous and less useful device for this kind of transportation over similar fleets of traditional or even electric bicycles, but that has definitely been the experience in cities where there is a choice. People are strange.
Either way, it is a low-cost and efficient means of transportation; all it needs is infrastructure to support it. While people are more than happy to lard the federal highway bill (and state equivalents) up with money to subsidize the single most dangerous form of mass transportation we have, the rare serious injury and the bumps and bruises related to scooters (and bicycles) turn into a big impediment to spending comparatively little on supporting infrastructure.