wear means 'have on one's body or a part of one's body as clothing, decoration, protection, or for some other purpose'
So - "I wear a moustache." You can see it on my face.
If you see a bullet hole in the head of someone's dead body, they did not grow or apply that hole/put a gun to their head and make a bullet hole for a fashion statement. The statement 'wearing a bullet hole in his forehead' makes it sound as horrific as: "My God. He's wearing a moustache. Some depraved maniac from a film studio make-up department must have attacked him and put a false moustache on him."
'wearing a bullet hole in his forehead' is the oh, so cool way of saying 'he's been shot', as if it is as everyday as saying 'he's wearing a moustache'.
No woman coming into a room, seeing the corpse with a hole in its head, and with the horror of it, doing the mandatory scream: this is 'cool', blasť private eye/private detective/gumshoe colloquial speech! Seeing a bullet hole in a head is as routine for them as noticing that someone is wearing glasses.
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