We always purchase travel insurance. Although we've never had to file a claim, my parents have had to do this when a medical issue arose. (All is well, thankfully.) Their insurance was set up in a way that covered their traveling companions, also. This is another reason I advocate working with a professional agent.
We were fortunate on our last cruise that we didn't need to use our insurance. Our ship left from Barcelona soon after the volcanic eruption that shut down much of air traffic in Western Europe for several days. Our flights were not affected -- yet, had they been, we would have been covered. The peace of mind alone was worth the cost.