Far be it from me to contradict your cabin steward, but allow me to quote from both Royal Caribbean and Celebrity's on-board Industry guides:
Q - "Are there irons and boards in the stateroom?"
A - "No, but there is a full laundry service on-board."
Q - "Can I bring my own iron on-board?"
A - "No, for safety reasons irons are not permitted."
Q - "Are there Irons and Boards in the Staterooms?"
A - "No, but there is a full laundry service on board."
Q - "Can I bring my own iron on board?"
A - "No."
You will find similar prohibitions in many cruise line's literature and in all of their Industry Advisory materials.
I think it is a disservice to those new to cruising to casually make light of what can be an extreme safety hazard on board. Leave the iron at home. Get a steamer or spend a couple of bucks and have the stuff pressed by the valet service.