Because humans suck ass at preventing harm. When cars were first introduced, they were implicitly allowed free roam over streets that were full of pedestrians,

Because humans suck ass at preventing harm. When cars were first introduced, they were implicitly allowed free roam over streets that were full of pedestrians, horses and carriages. They injured so many people they stopped counting, and each month would bring dozens of deaths. Only after enough people had died did they invent stop signs, traffic signals, lane markers, and one-way streets. They had to create new police departments to enforce the law on the road, and new courts to process offenses. They still didn't have mandatory driver education, brake lights, or posted speed limits. Left hand turns were difficult, drinking and driving was common, and people didn't understand why taking a corner at high speed might flip a car over. There were literally decades of people (mostly children) killed by automobiles on a regular basis, usually by reckless drivers and exacerbated by a lack of planning. And yet, even though some drivers would be pulled from their cars by angry mobs, nobody seemed to question whether all people should even be allowed to drive a car. Rules like crossing the street at designated intersections were created to put responsibility on pedestrians for their safety. By the mid-1920s, after two and a half decades of driving, we finally adopted national laws regarding driving, with driver education coming in the 1930's. Can you imagine if we let just anyone fly a plane? The sheer scope of the damage done makes even the idea laughable. But once the technology becomes cheap and available, it will happen, and we'll run into the same stupid problems. Because we suck at keeping people safe. Once automated cars become reliable and widespread, we're probably going to outlaw driving yourself, because it literally makes no sense to give a human total control over a two ton mass of steel hurtling down the road next to pedestrians and cyclists with no protection whatsoever (a curb is a guide, not protection). I mean, we don't even install metal bollards around cycling paths or sidewalks.