Sure they’re just a hazard to themselves on roads. The problem is that they are used on a wide range of paths, many of which have no real speed regulations of their own. So what’s to stop some yahoos from blowing through a multiuse path at 30 MPH (50 kph)? And that’s far more hazardous than other human powered transportation like bicycles, which have better steering and stopping distance.
Sure they’re just a hazard to themselves on roads. The problem is that they are used on a wide range of paths, many of which have no real speed regulations of their own. So what’s to stop some yahoos from blowing through a multiuse path at 30 MPH (50 kph)? And that’s far more hazardous than other human powered transportation like bicycles, which have better steering and stopping distance.