Meanwhile, motorcyclists are killed all the time by oncoming drivers turning left across their path

Yeah, I've been involved in one of those. Driver was traveling at more than twice the speed limit. Had he been traveling only 20 over, he would have been where the driver would have reasonably been able to see him. But he was traveling more than twice the limit. The driver couldn't foresee that he would cross his path. Couldn't even see him before it was too late to stop his turn, or for the motorcyclist to evade.

Car was totaled. Motorcyclist went to jail.