If people were told and not handed a letter they would complain that they never heard about the change. Why were people crying, yelling and calling home to find out where Labadee was? Someone at home tells them and then what? I am sure a Princess rep could have told them more than someone at home.
We all have different expectations, objectives, and opinions. After being on 6 cruises I would be content with not stopping at any islands. To me all of the islands are the same and some just worst than others. They basically have the same tours and are after the tourist's money. I just want to relax and not be hassled into buying something. I know that a lot of passengers like to snorkle, scuba, and do some duty free shopping. So a missed port could be a dispointment. If you are cannot be flexible then don't cruise during the hurricane season. You mention that Sandals will give you free days if you are disrupted by a hurricane. This is because they are not flexible. They cannot move their resort out of the way of a hurricane like a ship can sail around it. If Sandals did not have this policy no one would book during that season.
I have paid full price for a ticket to see ball games, NASCAR races, and amusement parks to have them shortened by rain. No refund or discount toward another ticket because the full 9 innings were not played. This is the chance you take.