Apologies, but to me, Dive Insurance and Travel insurance should be coordinated closely. . . .
I don't understand your reasoning. Your example above, in which you incurred $60k in air ambulance costs and another $60k in treatment, is the reason just about every diver agrees that accident and medical insurance is a no-brainer. That kind of money is beyond the amount of cash cushion most of us maintain in our bank accounts to cover miscellaneous misfortunes in our lives.
But I can't imagine how one could find themselves out of pocket $120k or even $60k in unusable airline tickets, a few extra nights in a hotel, meals, lost luggage, re-booking costs, etc.--the things typical "travel insurance" covers. Many of the things we tend to worry about are refundable, cancelable, or haven't yet been paid in full. Even liveaboards will often give you a credit toward a future trip. Travel insurance may be comforting, and as with any gamble it will pay off for the minority (anecdotes in which someone said their travel insurance paid for something are easy to find), but I only consider insurance a true no-brainer if it covers misfortunes that would ruin or nearly ruin my finances if I had to pay out of pocket. Medical care is a different animal from vacation costs, in my opinion.