Trip cancellation insurance is an option to avoid last minute cancellations on tours, cruises, etc. due to covered reasons. Airline tickets while nonrefundable, are re-usable for a fee. Delta can make decisions to waive fees on airline tickets because it is their product. They don't have to take into account other entities. Tours, cruises and similar things involve other entities that expect to be paid. They are not in business to make exceptions for people's personal issues. It is a risk you take when you do not buy insurance to cover unforeseen circumstances. I think WorldVacations insurance can be purchased anytime up to final payment. They also have "cancel for any reason" coverage.

Not sure that any insurance company will sell a policy when they know they will for sure have to pay out (pre-existing conditions). I know at least one cruise line (Regent) that will not cover pre-existing conditions no mater when you purchase their coverage.