When you think about insurance, there are different preferences about what you want to insure... trip interruption? Bag delay? Medical in a foreign country? Evacuation? Cancel for any reason? If you are looking at insurance, what is important to you to cover? We have used our purchased insurance on all of our past three cruises- trip delay coming home from cruise, medical issue while on the cruise (ummmm, dance party foot injury

) and just this week, cancelling for medical reasons.
As lane judy posted, the Chase sapphire cards do have some trip interruption or cancellation protection but it is limited and DOES NOT cover any preexisting conditions. I am in the midst of using our separately purchased
trip insurance policy, which does cover preexisting conditions, as a pre-existing medical condition is preventing us from going on a cruise in a few weeks. It is a relief to have the coverage. My chase sapphire reserve, used to make all of the payments, would not have covered our specific reason for cancelling.
A few years ago we purchased the Costco insurance. It covered pre and post cruise travel/hotel stays and we ended up using the policy as we had trip/flight interruption on the return home. It was very easy to use. However, I think that they changed the policy so that it only covers the cruise, not any stays prior or post. Just check what the policy states prior to purchasing. We did get pre-existing coverage by purchasing our policy within 21 days of initial cruise payment.
Insurance is cheap compared to the price of the cruise. Just think about what you want to cover and enjoy your cruise!