Most hotels give customers door tags with “Do not disturb” written on them. I don’t understand why. It’s obvious that no person ever wants to be ever disturbed. If you think that it’s something about cleaning the room, it isn’t: hotels give out these tags even when you’re staying for one night.
Plus, in hotels with actual keys, you give them to the reception when leaving. So they know when you’re gone. In those with plastic cards, the hotel knows I’m in my room as soon I as open the door.
I am in one of these today, and there’s a button instead of a tag. The button works only when I have my card inside the slot (I tried the business card approach; everything works only when the card is in there), so I got a second card. And as soon as I come back from outside DND is deactivated so I have to press the button once more. This button would be super useful if it would physically block the door from being opened by hotel staff or anybody else with the key, but it just shines a barely noticeable LED.
P. S. Does the Ritz Carlton do this?