It certainly appears that the CIG wants tourists who drink $25 margaritas out of souvenir glasses and then move on more then they want tourists who stay for a week or two and dive.
Lets look at the numbers for Key West. Every cruise ship that pulls in pays the government $10 a head for a landing fee. That means Tthe city of Key West makes $120,000 on a day that 2 cruise ships are in town. Additionally, the pier owners (oh, the city of Key West and the Westin) make an additional $10 a head for docking fees. That's a quarter of a million a day for a 3 cruise ship day. Those cruisers spend an average of $50 a day in town. That was from a study done by NOAA a couple of years ago, I'll look it up if you need proof. They don't use any of the town's services, all they do is hammer the reef. They buy booze cruises on Fury, Sunset, and Sebago at $100 a pop. They buy 3 t-shirts, and 6 Bud Lights on Duval Street, and they go away by 6 PM after missing Sunset, the best part of Key West.
Those who come for the weekend spend an average of $1,000 a head for the weekend. The city generates no direct revenue from this.
Those who come for a week spend an average of $2500 a head. The city generates no direct revenue from this.
Who do you think the city is going to cater to?
I don't have any idea about the numbers for Grand Cayman, but I would bet that the results are similar. I would hazard a guess that the cruise ship companies are spending a ton of gold to help push the cruise ship piers through, and will help in construction costs, because going pierside is way better then tendering ashore (in the eyes of the cruise line). They may destroy a bit of reef in the construction, but there won't be near as much blowback as from this video showing chain damage to a reef that falls something short of "pristine" in my eyes.
Piers are a win-win for the cruise lines, and cruise ships are a win-win for the government. I know we love to hate cruise ships for any number of reasons, but look on the good side. I've never lived anywhere where the property taxes are as low as they are in Key West. The cruisers come, spend a ton of cash (not individually, but as a herd), and leave by nightfall. What could be better than that, would you rather see 10,000 divers a day on Grand Cayman's reefs, with the associated infrastructure that goes with that, the sewage treatment plants and the hotels on the beach and the 2 stroke oil in the water?