Why is is so important games run at 60fps?

[Grey Acumen]

I think people also need to keep in mind the difference between a frame rate that we can discern individual frames, as opposed to a frame rate where we can still consciously register the change from one image to the next, as opposed to a frame rate that we can still SUBconsciously recognize the change from one image to the next. they're all going to be different frame rates.

If I were to hazard a guess, I'd say that 12 FPS is the highest frame rate that most people can discern individual frames.