Many people skip the passport because they are trying to save a few bucks (what is it now around $100?) With a family the cost does add it. But here is a situation where it is could be penny-wise and pound -foolish. Nobody ever thinks they will do anything but return to their port of embarkation on board ship. But stuff happens.
[of course I have to hide the DW's passport to keep her from jumping ship
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014, 2016
Star Clippers: Royal Clipper 2015