The reality is, this is a tradition of cruise industry - yes, they can make the wages/salaries adequate, then the tipping is not necessary - but that would mean your cruise prices would be much higher than now. You go the premium lines such as Radisson 7 Seas, Silver Wind, or Carnival's Seabourne (the one came in contact with Pirates off African Coast not too long ago), your cruise fare includes not only tipping, but alcholic beverages, some shore excursions as well. However, the costs of same itinerary would be 4 to 5 times higher than you would pay on a lowly Carnival or an old RCCL ship. The mass market Princess, Holland America, RCCL, even upscale Crystal all require tippings.
PLEASE DONT BE CHEAP !