Which country do you live in?
This question has been asked so many times..... But here it goes!
If you get off the ship and you get left behind or god forbid something terrible happens and you can no longer sail, YOU WILL NEED them to travel!
What good would they do you if they were left on the ship? Why bring them if you don't plan on taking them with you?
I ALWAYS bring ours off the ship, and never had a problem. Just treat them like your wallet or a credit card and you will not have a problem ...