we have been on 11 cruises with DCL, 3 of them we did not use Trip insurance, 2 cruises we used insurance through Disney and the rest we got our own through different means.
Things to consider... DCL insurance only covers what you purchase through them. When we shopped around we had to get different policies because MIL lived in a different state and she was over 70, so that changed what insurance you can get.
The times we did not use insurance, these were quick trips, we didn't travel with anyone who we felt might cause use to miss or need medical attention.
The only times we have had to use the insurance, was both times we had used what was offered through Disney. First time, DH went into the hospital 2 days before the cruise, we got the cruise money back and rebooked for another date, but airfare we were out the change fees for the airline tickets since that was separate. At that time DCL was using Allianz and we had no complaints was in 2009 and had to do everything via mail.
Last time, we had booked everything through DCL (Airfare, preCruise Hotel Stay, transportation and
Adventures by Disney add on), too big of a bill to let go by without insurance. Insurance was 2% of the total expenses. On the day of travel I got sick and was not allowed to board the plane , so we had to postpone travel for a day. Insurance covered, Hospital, Ambulance, airline fees, missed transportation and Pre Cruise hotel as well as expenses. Luckily we got to go on the cruise. It was fairly simple to work with the insurance which was AON Alliance and everything was done online.