And the eye's periphery, while it isn't sharp, is highly sensitive to movement. Which is "obvious" if you ponder the question where dangerous things appear first. Thus things dangling from the rear mirror in a car are a bad thing, they need (subconscious) attention.

The cone cells in the eye's center are color sensitive, but need a lot of light, while the rod cells at the edges are highly sensitive to motion, even in low light. And that might be one of the reasons why flicker is strenuous for the eyes. Funny side effect is that looking at stars in the night sky seems to work better when you look slightly besides a star, I guess that's because then the low light parts take over.