Uhm - MarciaLF: this service charge on NCL ships is NOT new (making it non alterable is new). NCL has been doing this for a while. And believe me the crew are receiving it one way or the other. NCL is not keeping it and using it for other things. BTW I asked a couple of crew including cabin stewards and waiters in the dining room - they all prefer service charge because they can count on getting something. The old tipping system was hit or miss.
My understanding from what the crew told me was that they get a certain base percentage depending on the number of passengers + extra incentive money. The ratings cards help to determine which "teams" get extra incentive money (which is why if you want to single out a particular crew member those cards are especially important).
If there is an NCL Crew member out there, please correct me if I misunderstood what I was told.
BTW : I am talking about the "service charge" NOT the "resort fee" on NCLA ships. The "resort fee" is completely different.