Except that's now how human visual perception works. Movement is distracting and one of the main reason people hate banner ads (which historically have been extremely attention grabbing, occasionally resorting to strobing for maximum attention).
Our brains are geared for paying attention to things that move, especially things that move irregularly (like poorly looped gifs).
We're particularly attracted to movements outside the focus point, that's what makes it distracting. The retina cells (mainly rods) further away from the fovea are bad at distinguishing things, but excellent at detecting rapid movements.
It helps noticing prey when hunting or predators when being hunted. It does not help when trying to read some text.
Our brains are geared for paying attention to things that move, especially things that move irregularly (like poorly looped gifs).