One of the trade offs for a cruise ship is if they stay in a port very late at night, then typically the casino cannot be open. And so there's obviously economic decisions the cruise line has to make. They look at how many dollars per hour they typically make when the casinos open. Cruise lines bring a huge number of tourists to the Bahamas, but the the casinos that are on the island (Atlantis, Baha Mar) don't want the cruise ship casino open because that affects them.

Japan is one of those places where they are strict on casinos. It's beyond just an overnight in Japan, where casinos won't open. It's at least between 3-12 nautical miles. The casino is not open because those ports are so close together, the ship doesn't get far enough out to sea..