It boggles the mind that some suit came up with the idea of calling the sailing service charges a gratuity and then had the idiotic notion to make it elective.
If we were in restaurants for three meals a day, surely we would be "tipping" more than what the cruise lines are suggesting. To tip a waiter in a restaurant a measly four bucks for a meal that would have cost you anywhere from $50 to $70 each would be an insult. But that is all they are asking of us. It is a part of our cruise cost. Yes, they should just put it into the price but unfortunately they want to spoon feed us into this new procedure.
When any of the ship's staff makes your passage special, please don't think, "my daily service charge covers that", think "I appreciated that additional courtesy and for that I will reward that individual" For your true gratuity, that given over and above the service charge, belongs to the recipient.