I don't ever get my room cleaned daily, but on a recent 6 day stay at a Marriott I wanted the room cleaned halfway through the stay (needed new towels) so I tidied my room and took off the DND when I left in the morning and... no housekeeping that day. Asked the front desk and they said.. it wasn't my day to get housekeeping since it wasn't the "every other day day" (lol?). I got some towels delivered that night so all was good and kept the DND sign up the rest of the stay.. and ironically on the 5th day the DND sign was not respected and they cleaned my room anyways. I asked the front desk why I didn't get housekeeping when I wanted it and got it when I didn't want it.. and they said "cleaning is mandatory after 5 nights."

Strange new world...apparently housekeeping is only done when the hotel wants it done now, not when you do.