You know they work hard and aren't paid much. Read here about why you should always tip your cruise crew members.
(By the way, we found a reference from 1908 recommending the elmination of tipping on passenger ships. The story goes way back. And it's something that's still discussed. In the meantime, it's the only way crew have to really make a living wage.)
(And did you realize that when crew serve events like the captain's cocktail party and loyalty cruiser club receptions, they don't get tips-unless someone hands them one, and that's rare. Read about this issue from the crew perspective by clicking here.)