I think Hertz is the only one that includes liability insurance with your rental. A few others used to include it but not anymore. I actually don't think it is mandidory for any rental agencies on either side of the island to offer this coverage free of charge. Lots of things on the islands are different from other countries. Lesley Bruce knows the rules for car rentals. If it was covered by the agency, the rental prices would be much higher. This way you can add it to your contract if you so desire. Some do for safety sake and some don't. It is an individual choice.