If you buy the most expensive DAN Enhanced plan ($200/pp for me), you also get coverage for >Medical< trip cancelation for you and your travel partner. $10k per incident. Unless you are purchasing trip insurance for every dive excursion, domestic or international, this is worth paying for.
I have now used this three times over the years returning about $20,000 dollars. The most recent payout of $10K was just this week. I broke my leg about 2 months ago, which was 1 month before a planned dive trip to Indonesia. The trip cost was a bit over $5k per person. The DAN coverage is for a maximum of $10K for trip cancellation. I filled out a simple form, included a doctors note, and they paid within 6 weeks. Fortunately, I got 90% of my airfare costs refunded, but I can make a credit card travel insurance claim for the non-refundable portion. Two other times my wife had to cancel on a trip due to other injuries, and they paid no problems.
While I've never had a need to call on DAN during a dive trip, they have saved me bundles over the years.