The reason those signs about there purchasing robes is because people steal them!. Port Orleans just opened the new Royal rooms and already 5 bedspreads and 12 bolster pillow are gone (stolen), and a luggage bench shaped after the dog in B&B was found running lose in the parking lot. Apparently it didn't fit in the trunk
One might argue that they thought a robe was for the taking, but a bedspread or a luggage bench? I don't think there is any excuse for that.
PS: if you take an item from the room, you will be billed for it.