I've been thinking about this episode and the NCL side is even more clear now. Why should they pay for something that was not their fault? If I was NCL, I'd rightly feel that the driver at fault for the accident bears the responsibility for the lost cruise.
I recently resolved things for an accident that almost killed my wife and son in 2006. My medical insurance paid the fare during my wife's long hospital stay but they required reimbursement when everything was settled - and they deserved it since my wife was not at fault so our insurer should not have to pay. This is no different than the case presented by the OP.