Just one diving accident, no matter how small, if it requires recompression therapy can bankrupt many people.
In Canada we have a public health plan that is supposed to cover me. I checked into it and found that yes they will send me off for recompression therapy, "if an attending physician considers if necessary". The problem is most attending physicians have little to no knowledge of diving medicine, and I will end up waiting in a hospital for precious hours till the "ONE" doctor in the city who is qualified to send me off does so. I for one do not wish to wait, risking permanent damage, just because the system is not ready for this kind of accident. With DAN, my public Medicare system is side stepped and my needs are taken care of by professionals who know what is going on and how to treat me. If it requires an airlift to the chamber, it is taken care of.
If you travel without DAN insurance on a diving vacation, you need your head examined. The membership is cheap, and the premium plan is very cheap for what it gives you. If you do not travel, and have a diving accident at home, the only difference from having an accident away would be your location. The rest would be the same, so my advice is to buy it online now. The online purchase process is fast, and is how I have purchased my insurance.