when you say them, it's a very very small percentage of pax. You'd see the same on other cruise lines as well. As stated above just avoid the 3/4 night ships on any line. You are way overthinking it .
How can I find a Carnival cruise that has 3rd/4th free? This would be ideal for taking our grand daughter. We only cruise as a couple so never really paid attention to this.
I just did this last week. Changed from Jubilee to Mardi Gras one week later. Cost was $50 pp to change. Also if the cruise you switch to is more money you need to pay the new price. Just an FYI: there was just travel update for the Bahamas as well.
https://travel.state.gov/content/travel/en/traveladvisories/traveladvisories/the-bahamas-travel-advisory.html