I have my 1st cruise coming up in May 2020. I wasn't sure what was needed to cruise so I read everything on Carnivals site (about everything not just travel docs), I talked to my PVP to make sure I understood everything correctly, I researched with Google as well as read different posts on fb and cc. Why take chances with someone possible giving you wrong information, always check more than once and with more than one source.
Even though I can take my trip with my DL and BC I will be getting a passport, mostly bc if something happens while on the cruise and also why do I want to carry 2 documents, 1 being just a piece of paper easily lost or destroyed when I get just take 1 thing, a passport. (I won't be driving). Plus a passport is good if you decide you want to go to Mexico or Canada, especially since I live in a border state.