If you’re talking about domestic travel within the US your post title doesn’t say that, but you’re right they are not requiring it yet. Have you you heard that they are somewhere?
“In America” covers boarding international flights because you are in America when you board, and Depending on the country you’re traveling to some places require the authorization before you board. Because they would turn you away at customs in the country you’re traveling to. And yes cruise lines are asking for it because you’re traveling out of the country many times to tropical jungle climates.
As an American citizen when have you ever been required to show proof that you have these to get on a plane, cruise ship, go to a sporting event, etc?
If you’re talking about domestic travel within the US your post title doesn’t say that, but you’re right they are not requiring it yet. Have you you heard that they are somewhere?
The part that says "in America" in the title isn't saying it? Yes, cruise lines are already saying it.
https://www.usatoday.com/story/travel/cruises/2021/04/05/norwegian-cruise-line-require-full-vaccinations-passengers-crew/7089216002/
“In America” covers boarding international flights because you are in America when you board, and Depending on the country you’re traveling to some places require the authorization before you board. Because they would turn you away at customs in the country you’re traveling to. And yes cruise lines are asking for it because you’re traveling out of the country many times to tropical jungle climates.