Perhaps some sort of instinct. Like, when you see someone vomit usually that will trigger a gag reflex. Because if you’ve eaten the same thing and one person got sick and threw up, your body knows it is better for you to vomit up the poison before it really hurts you. (There’s not really a way to explain to your body that you aren’t foraging in the wild, eating all the same stuff anymore.)
So in the same way—you see bugs swarming, and the instinct is to itch and twitch to make you brush them off. Because your instincts don’t really know about movies or TV.
This is all speculation, mind you. I don’t actually know.