It's definitely both. If you ever want to feel completely invisible, get on a bike. People genuinely do not see you, even when they look directly at you. Obviously lots of crashes are the rider's fault, but even very careful defensive riders get hit by car drivers. Inattentional blindness is a real thing, and there have been plenty of studies demonstrating that drivers' brains simply filter out people on motorcycles a lot of the time. Anything that helps prevent that is going to save lives.