Something not mentioned, but worth understanding, is exactly what "refundable" and Non-refundable" tickets, as well as several other options actually means.
In many cases, refundable vs. non-refundable simply means that if you need to cancel, you get cash minus a handling fee (could be a couple hundred) back, for non-refundable you get a credit, minus a re-booking fee. If you are planning on travelling again, there may be little difference.
I think you need to separate out trip cancellation insurance from Medical/Evacuation insurance. The medical is simply a risk you need to assess. Trip cancellation though is tougher in my book to justify, only because, as others have mentioned, if I can't go, I am able to cancel or rebook at little cost. Now if I shelled out thousands for a tour, that would be different. But the typical independent traveler may not have many issues, especially if you look at coverage under Credit Card amenities.