I am guessing that it’s different because they spend weeks and months on the ship. I don’t know about you, but I wouldn’t be too keen to enlist in the navy if it required not having my personal phone for months on end. They gotta make some concessions in policy to keep everyone sane.

Or maybe they’re banned but people sneak them in anyway.

Edit: then again, if they just snuck them in, they wouldn’t have any connection. They need wifi. So it’s probably allowed.