Why? To make it harder and kill you, that's why. Literally the only reason I can conceive of given how traps are overused. Why put things somewhere for safekeeping and then make it so you are almost certain to die retrieving it yourself. It's not like there's an off switch or something.
There weren't even any valuables there! It just laid awkwardly on top of stairs leading to an open area, and that was after a tough-ish fight with a beholder and a drow
I threw a corpse at the vent to plug it. It didn't work. I walked through it anyway and took 2 damage lmao
