It's rare to cut it short; more likely, they will change the ports or do an additional sea day instead of a port so they can navigate around the storm. In 2017, I was booked on a 7-day Eastern the week after Hurricane Irma. They ended up canceling 3 cruises the week of Irma, and they changed my cruise to a Western, not Eastern. I was not thrilled with the Western, so we called and they let us change it to a Mediterranean cruise the next summer. So...if it's totally canceled,
DCL will refund you with no effort or insurance necessary on your part. But more likely, they'll try to change your cruise ports instead of canceling the whole thing. So if you're OK with them changing the ports or adding extra sea days, then you're probably fine without insurance.
Another issue to think of is if you're flying to the port. If there's bad weather, what if your flight is delayed? That seems to be more cause for concern to me than the actual cruise being disrupted.