Because this has not much to do with what Waymo or Tesla are doing. What they've developed here is a control system, a way to make the car move in a certain way

Because this has not much to do with what Waymo or Tesla are doing. What they've developed here is a control system, a way to make the car move in a certain way, follow a certain course. The problem that autonomous driving needs to solve is to have a car that can reliably perceive and understand what's happening around it, navigate any complex situation involving pedestrians, intersections, road work, parking, etc. The drifting DeLorean doesn't have to worry about any of those things, it only has to work in an empty parking lot. There might not even be safety measures to prevent it from hitting people. They use precise GPS to track the car's position (where it is on the course), so it's possible the car doesn't have cameras or LIDAR to perceive its surroundings.