We're usually Royal C customers, but ports and itinerary on a particular Princess cruise fit our schedule best for this summer. We booked through Princess, were offered Trip Insurance, but declined (we're not stupid - our Credit Card offered free trip insurance).
Three weeks before our cruise date my MIL became hospitalized and it appeared (true, it turned out) that she'd have to enter a nursing home for a while. We weren't in any mood to cruise; the question was, would TI cover us if she was no longer hospitalized by cruise time - no way to know if she would be.
Called Princess on the off chance they might offer a switch to a different cruise. Short and Happy story: they had apparently oversold our cruise, so they not only offered a switch, but gave us upgrades! Princess went above and beyond what we expected.
NO ONE should cruise without trip insurance. As others have noted, you never know what can happen, We got lucky; the OP didn't.