I sincerely doubt that service would suffer any more than it already has.
After 20 cruises from the early 80's to today, I can state, I have never received anything other than the service I would expect. The cabin was cleaned, my meals were delivered. Nothing out of the ordinary at all, certainly nothing I would claim to be wonderful or outstanding.
Your mileage may vary of course.
For the most part, I think many people tip because it is expected of them, nothing else. I've read lots of comments to that degree here.
I think that most of my problem, with cruises anyway, is that WE are THE source of their wages. If we do not tip them, they will basically be penniless.
That is my real issue!