Most drivers have years or decades of experience in watching cars with unconscious acuity, and being able to track them without even realizing it via their peripheral vision. All of those skills go out the window when they are confronted with a bicycle on the road, and the need to constantly make conscious checks on the bicyclist generates stressors and tension that otherwise wouldn’t be there.

i believe the Critical Mass event was organized precisely for the purpose of challenging this idea -- suggesting that with a critical mass of cyclists on the road, drivers can't help but learn to notice and watch for them. this seems to work on a day-to-day basis in places like Amsterdam and Copenhagen. if the roads aren't safe because cyclists are rare, but cyclists are rare because the roads aren't safe... maybe let's work on making the roads safer?