I recently went on a Carnival Cruise, and I was pretty surprised at the audacity of the crew when it came to tipping. There was a "seminar" on the second-to-last night in which the crew told us how much we were expected to tip. Then the envelopes showed up in my cabin...
That's not tipping, it is responding to a direct solicitation. Carnival doesn't want to pay their employees, and instead wants the passengers to pick up the tab in order to fatten the profit margins. Automatic tipping is simply a service charge.
The thing I had the biggest issue with, was the 15% "gratuity" added to every drink purchase, including soft drinks. Good luck getting a bartender to serve you a drink! This is an absurd policy, considering that most people would drink more if this "gratuity" wasn't added to their bill every time.
The trip was part of my honeymoon, and we had the best cabin on the ship. Nevertheless, we had to wait in line with everyone else for 2 hours to board the ship (and disembark for that matter). There were no special elements added, such as free champaign or chocolates in my cabin. The room steward spoke no English. I expected a queen bed, and got 2 twins. So I was irritated from the get go, and wasn't feeling real generous. Carnival is the K-Mart of the high seas, and I wouldn't be caught dead on another one of their ships.
I'm actually a pretty generous tipper, and the best way to get me to tip, is to not ask for it.