Why not skip a few steps and just electronically limit the top speed of all new vehicles? Too much revenue lost??

A: they do already. Either electronically or via gearing and rev limiting. B: you may want to exceed the speed limit to escape danger. C: not everyone uses their vehicle on public roads and there are places you may want to do over 100 mph, like a race track. Side note, some vehicles know when you're at a track. Sometimes that feature doesn't work. D: it's not practical. What top speed would you set? In NY, it's 65. Montana is 80. Texas has a highway where it's 85. What about Germany? A maximum speed does not keep someone from doing 60 in a 30.

Dynamic restrictions would also be a problem, either by forcing location tracking into every vehicle or relying on (eventually) outdated database or flakey computer vision (cameras can get dirty). Then you need to consider what action to take when a vehicle is exceeding the speed limit. Are you going to disable the throttle or apply brakes? How soon and how hard? Keep in mind that older vehicles don't have this system, so braking may cause an accident. Disabling the throttle might also cause an accident either by upsetting the car with unexpected weight transfer or indirectly because the car could not get away from danger.