Why? You can kill a pedestrian, bicyclist, or motorcyclist just as easily with any of them. Why not improve the drivers test to actually test people? That should cut down on accidents across the board.
I agree that U.S. states should provide far more driver's training and have much stricter testing requirements before issuing licenses. We also need additional tiers to our licensing.
Two examples: In my state, a sixteen year-old with a newly minted standard car driver's license can by themselves legally operate a loaded 26' box truck, including one towing a trailer. With a motorcycle endorsement, they're permitted to pilot a bike with an engine of any displacement.
Ok? The motorcycle endorsement is already a separate tier. I don't think there's anything wrong with operating a box truck on a regular license. There's not that much difference in vehicle operation (still hydraulic brakes, etc), just some additional emphasis on load distribution, engine braking, and speed/braking distance - which is still important in many smaller vehicles. I do think the regular license test should be more rigorous, since it doesn't even cover these topics sufficiently for the smaller vehicles.