I've actually worked for Hotel security at a top name hotel. Trust me, Housekeepers look for opportunities at at least the same rate as any other group of people. It's probably higher to to the easy and constant near-anonymous access.
Plus, as a guest I could have a lot of success during prime housekeeping times by simply posing as a room's occupant. Just wait till houskeeping is in there cleaning (door is open) flash a room card and mention something about "just needing to grab my laptop off the table..." By the time I pretend to be trying to understand whatever they are saying, I'm halfway to the stairs. Easy.
There are many master keys in a hotel and many floaters that will also have access to your room, including other guests due to accidental room assignments. Then there are insiders who can clone out master keys, etc while teams will hit the rooms during the day. Then the lock pickers, hackers, social engineers getting room key replacements, etc etc. Still, the number one most likely threat is Housekeeping and maintanence from one reason: ACCESS
Never assume that the hotel is as concerned about keeping strict controls and records of your room access as you would be. Don't leave anything in there that would be devastating to you if it disappeared.
