I don't know about no tipping allowed but several of the luxury lines advertise and tout "no tipping required or expected". For the most part on those lines it's true and I actually think most crew don't expect tips. They certainly don't hang around toward the end of the cruise with that kind of doe eyed look of expectation hoping you're going to hand out cash. In 2012 we boarded the Silver Wind in Barcelona and were greeted later in the day by one of the bar supervisors. Turned out she remembered us from a few years before on Holland America's Oosterdam when she was a bartender. We talked off and on over the next week plus and the subject of why she'd left Holland America and gone to Silversea came up. She said two things lured her away and that was higher pay for shorter contracts. In several subsequent cruises on Silversea I have heard the higher pay, shorter contracts, and overall better working conditions repeated a number of times. Could be PR and they're just singing the appropriate "company song" but I believe it to be generally true.