Christine is right - the surverys ARE read. I have a friend (a musician) who has been with Princess for 12 years and he says the survey cards are most important to the staff and crew.
Although his job has been the same for 12 years, he has seen countless assistant waiters move up to waiters, then to bar staff and then to bar managers and on and on.
What does it hurt to take a few minutes to make some observations? Again, the percentage of the world's population who gets to cruise even once is so small, we should all feel very fortunate to be there at all. If we can make someone's future a little brighter, why not just do it?