As others have noted in this thread, our "dinner tips" to our servers are not just tips for dinner. Those tips (plus whatever they get from pooled beverage tips) are the servers' compensation for working from dawn until late night, 7 days a week, at breakfast, lunches, buffets, snack service, dinners, and late night snacks -- on the ship and on
Castaway Cay.
(Yes, they get some time off during the day, during non-meal periods, and not all servers work all non-dinner meals, but it's still more like an 80-hour work week than a 40-hour work week.)
Also, their tips are not on top of US minimum wage. Those tips are essentially their entire compensation, except for the $50 per month (or so) base that
DCL pays, and "free" room and board in small, shared cabins below the water line. Of course, it's likely they're still paying rent in their home countries so that their families, whom they don't see for many months at a time, have a place to live.
For the crew members, the pay is good compared to what they could get in most of their home countries. It's hard work. It means that their families have decent housing, food, clothing, and education -- especially in countries where the US dollar goes much further than in the US.
I don't think the guidelines are excessive. We tip well over the recommended amount, and I assume most other DCL passengers do too.
The tips to the Dining Room Server, Dining Room Asst. Server, Dining Room Head Server, and Stateroom Host/Hostess are a small sum compared to what we pay to DCL -- yet these hard-working people do so much to make our time at sea (and at Castaway Cay) so wonderful.
The dirty little secret in the mainstream cruise industry is that "all inclusive" cruises really don't include the cost of the dining service or stateroom service. The cruise lines expect the passengers to pay. This allows the cruise lines to keep their cost structure lower, which allows cruises to be priced affordably. As long as everyone understands the situation, it works out well for everyone.