Ya gotta do what ya gotta do! I would feel guilty if someone bent over backwards and went above and beyond and I did not reward them. I don't like feeling guilty or unappreciative, so I reward the service and the person who served me.
I'm sure there are some people who will look for any excuse to justify NOT even giving them the suggested amounts. That's their business, I wasn't raised that way. Heck I leave the hotel maid a tip even if I stay just one night!
I do believe, however that if more and more people don't tip even the suggested amount, more will be added on to the cruise price to make up the difference.