Like most car driver, including myself, we are conscious of what we see in front of our view. There image on both side of our eye and the driver have to made judgment call as to who is beside my car. For example, on the side of my car, I can imaging an image that go up and down in motion, I can guess that it is pedestrian walking. If vigorous up and down motion, they are probably running. If the move side to side and up and down motion, it is a cyclist. So the car driver have to get use to an image of an upright figure with any motion. And there will be the escooter/scooter rider.
The second issue is that more driver could not anticipate the speed of the escooter rider. While the escooter conclude that the car driver have seen and allow the escooter to go faster. But the issue with most driver is that they do not anticipate the scooter to go fast. Hence there is an error of judgement in speed. This could result in collision with the escooter rider. This will occurred mostly in the busy city streets as various commuters will negotiate the right of way.