It would be much worse if they had given a key to another guest thinking the room was unoccupied and the guest had entered the room.
That happened to be once. The property didn't communicate my 4PM late checkout to housekeeping, and they cleaned out all my stuff. While I was waiting in my room for my stuff to be "redelivered," another guest waltzes in. I'm told him sorry, I have this room til 4PM, and to please tell the front desk that you were traumatized by the experience of walking in another guest, and that they should bump you up to a presidential suite.