NCL is attempting to keep "sticker shock" at bay. The $10 service fee is as much a part of your tab as the cruise ticket is. They started this policy with Pride of Aloha crediting the extra cost of the all-American crew. Now it is to be applied to all other ships, which don't have an American crew. They are paid around $50 per person, per months. Some of the $10 fee will go to them, but I'm not all.
Ships are full now and cruise lines don't have to lure you with lower prices.