[Summary: Many a times we are forced to cancel our travel plans, mostly due to an emergency which can amount to a huge loss if you are not insured. Your travel insurance policy will have certain conditions regarding trip cancellation.]
Life is unpredictable. This makes travel insurance is essential for those who travel. It covers a person in the event of a medical emergency when traveling or in case the trip is cut short or cancelled. Policies also cover lost luggage. Travel insurance will often cover expenses related to unexpected cancellations by your carrier or destination providers, e.g., costs associated with a canceled flight, including accommodation, meals and other incidentals. Cancellations due to emergencies are often also covered; some possible examples include medical advice telling you that you cannot travel, a death or medical emergency in your family, a major disaster at home such as a house fire, disasters or upheavals at your planned destination that occur after you booked your trip. Depending on what's happened, the travel insurance company might pay re-booking fees, refund lost deposits, or pay for travel home. Travel insurance pays only for direct losses such as these; you won't get additional compensation for things like your disappointment at your holiday being cancelled.
More expensive travel insurance policies may also cover your own discretionary cancellations if there is an exceptional circumstance. There is always a raft of conditions about acceptable and unacceptable cancellations. You can purchase travel insurance covering a trip home because of the death of a family member, but a trip home due to the death of a friend almost certainly won't be covered and even a de facto partner's death might not be covered. Family medical emergencies other than a death often aren't covered; for example the travel insurance might not cover a trip home to be with a family member who has been hospitalized or diagnosed with cancer.
Many travel insurance policies cover cancellations or delays due to terrorist activities. If your transportation carrier shuts down, you may not get paid unless they declare bankruptcy. Most policies will not cover a strike if you book travel after union members vote to approve a strike. Also, be aware of de facto strikes such as a "sickout"--usually by just one segment of the airline. A few travel insurance policies may not cover this or cover it only as a delay. Some policies cover cancellations if a destination has recently become unsafe due to either a declaration of war or a recommendation by your government to cancel travel to a particular area; others do not cover this.
Take care with cancellation waivers offered by tour packagers or operators and travel packagers or consolidators who've arranged your travel. If you or they must cancel, such waivers typically cover only what you've paid them, and not other related commitments you've made. They also will have no value if the reason for cancellation is bankruptcy of the packager or operator.