Human eyes have incredible detail on where they are focused. A human will look to where the road is in the distance and see high detail of what is approaching from that exact position. A single side camera has a wide view of the world, so all the pixels are spread over the entire scene. There is no way to focus in on just where the road in the distance is. Keep in mind the road in the distance will appear in different parts of the image, depending on curvature of the road and elevation changes. i.e. it might appear high up to the Tesla if the road is coming from a hill. This is why you need incredible detail from the sensor, because you first need to determine where the road goes in the distance, and then focus in on that particular area for processing. Using low resolution images to try and determine objects at distance is subject to significant corner cases. For instance cars that are a similar colour to the road may appear to be just the road when sampled at low resolutions.