There can be several reasons to cancel a ticket but cancelling a non refundable ticket can be a costly process as you can lose your money if you don't get the refund. The non refundable tickets are comparatively expensive then the refundable one. The airlines charge more for a refundable ticket then they charge for the non refundable ticket. It is the main reason that people choose non refundable tickets over refundable tickets. Cancelling a ticket totally depends upon the situation of the individual. Sometimes there are situations in which you can not travel.
For example in this pandemic scenario the person who isn't feeling well or has fever or cold or even they are corona positive. These people cannot travel through flights or any other transportation. So in this situation an individual has to cancel their flight even if they have a non refundable ticket. Some people have to cancel their ticket when they lose their job. If the individual is terminated then they also can not travel and many other reasons.
The person should immediately contact the airline's customer service because the airlines might know ways to help you. The main point to keep in mind is that you will not always get the refund. You might get a few portions of the ticket amount but it is not guaranteed that you will get the whole amount back. They deduct their service charges if they are giving you the refund.
Yes, there are few methods from which you can get your refund as well:
WISH TO HAVE ANY NATURAL DISASTER: this might sound like a funny method but this can actually work sometime if you are sure about your cancellation. If there is any bad weather due to this the airlines can be delayed then the person canceling their ticket will get the refund as well.
BOOK THROUGH A TRAVEL AGENT: if you have booked your ticket through a travel agent then it is convenient for you to get your ticket cancelled because they have a lot inside connections.
RESEARCH: if you do the research properly then you can compare the policies of different flights and choose the right one.
You can cancel your non-refundable booking but if you want a refund also then it is only guaranteed in the nonrefundable tickets only.