My nightmare scenario is being on an uninhabited island or some other far flung locale, away from help, and running into some bad guys while I am alone with Cate. Use your imagination, think about the worst possibility. That is why I would carry while cruising.
Someone stealing my dink or other boat stuff would not necessitate me shooting (at) them, just "life or death" pirate scenarios where help is unavailable. Nor would I draw a gun on someone breaking into my boat while I am sleeping in a marina in the states.