we take passports off the ship because it feels foolish not to.
I've been to Mexico, England, Scotland, France, Netherlands, Germany, Austria, Switzerland, Italy, Monaco, Vatican City, Spain, Liechtenstein, Morocco, South Korea, Canada, Japan, Bahamas, British West Indies, Norway, Sweden, Republic of the Marshall Islands, Russia, Denmark, Finland, Belize, Honduras, China, Singapore, Qatar, Nepal, USA and we have a trip book to Peru this June. I understand and the value of my passport and guard it with my life. The security briefing I am required to get at my company before traveling internationally told me the black-market price for a US Passport is about $25k. Taking the passport with you when it is not required seems foolish to me. YMMV
I guess we all make our decisions based on perceived threats and dangers.