Medicare is not designed to cover many things people here want it to be. Not even a regular commercial medical insurance.
It is a medical insurance that covers your regular medical needs when you are at old age, and by default, would need more medical care, such as long term diseases, cancers, diabetes, kidney diseases, etc etc
That is common sense, right?
If you want everything covers, from a long term stay aboard to a Travel Medical Evication - then you need to look at insurance that cover those particulr areas.