If everyone did that there wouldn't be any hot water for a shower. A portable steamer work like a charm. Putting clothes in a plastic bag before packing does wonders for preventing wrinkles. Some people say rolling your clothes instead of folding them helps to prevent wrinkles.
Get a can of Wrinkle Out...we use it all the time...and it really does work....but then again, who cares if your have wrinkled clothes..you are on vacation....Have a great cruise...