just can not understand why people would do more cruises or upgrade to a suite just so they can receive more C&A credits
What is hard to understand? It is more than a free hat and some drinks. Higher level membership means priority embarkation, priority debarkation for diamond level, complimentary air deviation if you use cruise line air, discounts on balcony and suite cabins. Those things make it worthwhile to get points. Granted, the cuts from the program are not huge, but they are things that diamond members were given and now have had taken away. Other similar program have grandfathered current members and only put new members under the revised program. Make a new level for the grandfathered members (Classic Diamond for example) so you can keep the groups separate. Celebrity did this when they revised their loyalty program. I was made a "founder" Captain's Club member which meant I kept the original perks yet new members didn't get them.