They are truly "no tipping" and at least on Seabourn, staff are discouraged from accepting tips from customers. The ship's maintain a "staff fund" and if passengers do want to tip, they can contribute to that. The staff purser and captain can then use the money for special treats for the entire crew (parties, etc.)

When I've had staff who have gone above and beyond, I've treated them to drinks if we run into them in town, brought them back treats from port (a lot of the young mostly European staff are also foodies themselves), or left good feedback on my mid-cruise and end surveys. The cruise line also recognized them with treats like shore excursions.