Basically, the laws say that your vehicle must be licensed to be used on a road unless it’s a bicycle/pedal assist bike/a few other categories, and there’s no mechanism for licensing some of the newer transport options. The laws also say that a vehicle can’t be used on the pavement at all, so there’s no way they can be used on a public road at all.

And have you ever seen a picture of most British cities - there’s barely enough room for cars and pedestrians sometimes, never mind a whole separate lane for cyclists/etc.