it's a fairly recent invention so regulations wouldn't even have considered it. regulations are made for casuals who ride very slowly and there's not a lot of thought put into it, for example in my country toddlers bikes are required to have a coaster brake because of some archaic idea about it supposedly being more intuitive to backpedal to stop (as if the kid isn't just going to put their feet on the ground if they freak out while learning to ride) and that toddlers supposedly lack the coordination to use hand brakes. and there's still some law about how technically you're supposed to use hand signals that came from a time when people rode horse carriages. it's common knowledge among serious cyclists that you should have MIPS or some similar system in your helmet. normies are barely aware that bikes can hit more than 20-30 km/h and most normies wouldn't pay much for a helmet if they buy one at all.