Some bike lights flash at low frequencies, with big gaps of dark long enough for a driver to look and not see.

^ As well as pedestrians.

To those who also drive cars: how do annoying flashing bike headlights affect you? Beside being annoying, does it affect your vision and does it potentially lead to accidents?

When I'm in driver mode, they help me notice the cyclist but otherwise do not affect me. The lights of other cars are much brighter.

I often ride along parked cars (yeah door zone, but I'm very careful and quite slow, and those cars mostely are parked there for extended time period), from time to time some careless pedestrian would suddenly pop up from sidewalks to the street between the parked cars, so a steady bright headlight is important to help alert them beforehand. A flashing headlight would not be so good.