My medical insurance covers me outside of the country, so typically, not for that.
We get medical evacuation when it seems prudent: a trip to the Galapagos, where self-insuring medical evacuation would be insane (whereas a trip to London or Montreal- eh, they have hospitals there); a cruise when I was pregnant- I wouldn't WANT to be treated in a Caribbean hospital, even for something small, while pregnant- so again, evacuation seems a good idea to have.
For the most part, we self insure. Yes- a huge medical emergency requiring evacuation would eat up most of our assets, but between our own and my parents, we'd be able to handle it. The chance of needing it is relatively small.
The Galapagos trip, we actually did file a claim- the insurance also covered trip interruption, and a fire set to the FAA facility in Chicago shut down nearly all midwestern airports the day we were supposed to travel. We got about $600 back in prepaid tours, meals, and hotel for the day we missed.