Other than a concept that strains credulity, and a way of getting at the divine, why might we be interested in non-being? It should be clear, from the range of senses of non-being that we've seen here, that it is a concept that serves as a description of a range of problems or issues, or it is a concept that serves as a solution to a range of problems or issues.
In some cases, non-being serves as a kind of limit condition for thought. It becomes the abyss that we stare into. During Romanticism in the 19th century, there was a sense of the irrational in human existence (and by extension, in all existence). It was where evil lived, where the non-rational parts of the self lived. It was Frankenstein's creation, it was the fear of the loss of human meaning in a technological world.
By the 20th century, it is also the sense that all change requires non-being. God, after all, is fully actual, and also cannot change in any way. There must be potential to change (which is a kind of non-being). Some, such as Sartre, take this much further than anyone before did, and see human existence itself as a kind of negation. We strive to define ourselves, to become actual, but the fact is, to the extent that we have freedom, we are in a state of non-existence.
Mysticism trades on the idea of non-being throughout its textual history, and as we've seen, it becomes relevant in different ways for different thinkers.
This link in Google Scholar will give you a sense of the range of uses of nothingness, non-being, and negation in scholarly work.