Why do normies have an obsession with “wearing underwear to bed?”

I’ve never experienced thirst for a girl in her underwear in bed. When it does happen it’s because of seeing her furtively preparing for bed with her thirst trap stuff and you don’t really notice the underwear bc it’s underwear and a shirt. I think it all came from an old movie saying “wear silk underwear to bed” and everyone took it like it was saying that seeing a f in her underwear is the most thirst thing in the world.