Thankfully that has never happened to us. On our last two cruises the stateroom attendant left an envelope with the luggage the next to last evening but not once has anyone mentioned their salary or outright asked to be tipped.
We carry cash and as I have stated before, bartenders and servers in the lounges get tipped on a drink or evening basis. If the dining room staff, stateroom attendant, butler, etc. go above and beyond then we give additional cash at the end of the cruise.