There are several reasons for trip cancellation that are covered. Essentially, this depends on the respective insurance coverage of the provider.
All insurers provide coverage in the event of a serious illness. Severe means that, in view of the symptoms of the illness, the start of the trip is not possible or not reasonable. The death of close family members is also insured.
If you are seriously injured before your vacation and need surgery, you will be refund. Also if your property is severely damaged, for example by a house fire.
Some providers offer even more comprehensive protection. They also pay if you have lost your job for operational reasons. Or if you start a new job and are still in your probationary period when you start your trip. If you are a student, you may be covered if you get the Date for a repeat examination during your vacations.