[geofft]

Again, it doesn't have to be mandatory from the government. It's just that the car companies guarantee they won't hit you if you have a beacon (i.e., they take on all liability), and they make no such guarantee if you don't (i.e., you or your bereaved family have to go fight them in court, have fun). They will have complicated spreadsheets internally calculating the "acceptable" level of casualties, where they can keep the public convinced that it's their fault for not carrying beacons, and not invest in improving their detection algorithms beyond that. (Engineers working for these companies will earnestly try to build the best algorithms they can, but senior management won't staff or fund these departments any more than necessary.)