Carol bought a basic travel insurance policy for her round-the-world cruise. While at sea, she experienced severe shortage of breath and was diagnosed as having pulmonary emphysema.
She required oxygen until the next port, where she was taken to the nearest hospital and eventually required medical evacuation to a better hospital. She didn't have adequate cover and ended up having to pay $90,000 out of pocket for the medivac and hospitalisation. She even had to borrow money from her children to help cover the costs.
* This is a fictional, but realistic, example.