most people here probably dont buy but I have bought a number of times
Bottom line -I dont recommend buying travel insurance for cancellation coverage because you can get it by using a CC. But you may need it for medical insurance.
If you buy a ticket and book with the right CC (not Amex) they will cover changes to itinerary due to illness(no preexisting), also baggage delay etc.
If you book with miles and only charge taxes they may not cover itinerary change costs eg Chase now has language saying they will cover costs if booked with Chase rewards.
If you dont have health insurance outside the U.S. then you may want to get it. Even if you do have, it can be very difficult to collect, its a paperwork nightmare.
I buy the insurance when I travel with my kids. On a few weeks trip someone is likely to need a doctor.
I have used Travelex Lite and recently Travel Guard. They cover kids under 19 for no extra charge with an adult. I cover one adult and all the kids.
I have a collected a few times from Travelex with no problem. Just get all the paperwork you can, the bill, a receipt, diagnosis etc. It doesnt have to be in English.
After speaking with them I learned you can play with the coverage amounts. So if you book a trip with miles and only pay taxes of $50, you could enter that as the trip cost. Or, you could enter trip cost as $500 and the kids trip cost as $5000 and it will get you some more coverage at the same price. They are fine with that.
Same for the dates of travel, you could enter a longer period of time. Say your trip is for two weeks. You could tack on two weeks at the end and, in case you are delayed. Otherwise the insurance stops when you were supposed to leave.