I understand the instructions for such fires is pour any fluid on it, do not use ice, use whatever is at hand....drinks from the cart etc. It may be the cabin crew were scared to use these as they feared getting their pay docked.
While I can understand the people taking their handbags,,,,,money passport etc it is about time that those that take those big wheely suitcases are met on arrival and arrested for disobeying Flight Crew Instructions by taking them.