Even with DND signs on the door, some housekeepers just ignore the signs. Given they often get paid by the room and want to get out of there as soon as possible to go to the next job, they may be in more of a rush to get guests to check out than they should be. Unfortunately, when guests are getting sleep disturbed like this, the chances of getting the hotel to provide a material refund for the wrecked rest or any other goodwill/compensation gesture seems less likely (and less generous) nowadays than it used to be.