We've done quite a few cruises and this is the first time I've heard of any cruise line giving a hoot about us having insurance or not. We always have travel insurance but I didn't think we could purchase 'miss the ship' type. US cruisers talk about 'any reason' cancellation insurance but I've never seen that offered here.
As to booking a resort while on a cruise, I do understand that, especially if you're far from home, a bit tired of the ship's 'pee pool' and fancy a nice beach day. Only once did we book a beach resort, in Jamaica, through the ship. It was poor, couldn't go in the water due to high seas, food was meh, but, at least, the rum punch was good.
Most of our cruises are booked to see destinations rather than beaches but YMMV.