The only reason not to book air through the cruise line is because it can often be more expensive. In general, it's always a good idea to make the cruise line responsible for your air as part of the whole package, then they are responsible for getting you to the ship (which just didn't work out in this particular case because of Spring Break, but as has already been stated they were ready to fly the OP to Jamaica to meet up with the cruise ship, which wouldn't have been the case if the air were not booked through the cruise line.).