My guess is that they don’t want to be seen asking for something they’ll publically fail to get. At this point, outside of the world of tech, people who were downright alarmed by SDV’s now have a place to hang their hat. Politicians follow the direction of popular sentiment, and they’re not going to risk the next Uber fatality having their stamp on it. They’ll be thinking the next corpse might be a child’s as well, and how that would hurt their prospects for re-election.
On HN there are a lot of Vulcans who have stats ready to go about human driver fatalities, but that’s far out of touch with the average voter. Fear = Dread/Sense of Control, and most people think they have a high degree of control as the driver of a car. I’m not arguing that they’re right, but they’re the majority.