For some reason zombie fiction always seems to take place in settings that are so wholly unlike the real world that no one knows about zombies. The Resident Evil game franchise, which I've been looking back at recently, doesn't. People are quick to point out that there are zombies and monsters.
But it still has a lack of people picking up on the fact that shooting the zombies in the head is the way to go. The occasional character will pick up on it (or at least say they have), but usually one who has plot reasons to know more about the zombies than ordinary characters. Otherwise, even when shots to the body demonstrably don't work very quickly and shots to the head are one bullet and done, the characters keep on aiming at the chest. This might make sense if they were horrible shots (no amount of aiming at the head and missing is going to stop a zombie while enough shots to the chest will stop a Resident Evil zombie, so if you're a bad shot go for the bigger target) but some of them are excellent shots and they still don't favor headshots.
But back to general zombie fiction.
Bad people are coming to do bad things and you've reached the point of lethal force. You fire a shot into the person's chest. Either they don't even fall, or they get back up again after falling. After you've shot them. At this point zombie fiction usually expects us to believe that you'll be confused and unsure of what to do next.
I quote Wash: "What about his face? Is his face wearing armor?"
The local police force might not be willing to make the leap to realizing that the evil crowd advancing upon them is made up of the walking dead, but after shooting people repeatedly in the body didn't stop them, wouldn't they at least consider the possibility that they should aim for the one place they know doesn't have concealed body armor shielding it?
Yes, zombie fiction, for reasons that defy explanation, takes place in a world with no zombie fiction (it's why Jaws was set in a world where no one had ever heard of sharks-- oh, wait...), but it seems like well before people reach the conclusion, "Dead people are walking around and biting living people," they should reach the conclusion, "Aim for the head."
Yet I can think of no instance where someone said, "They must be wearing body armor, aim for the head," in a zombie movie or game. I have not actually read zombie books.