To generalise hugely, with no small sense of irony, it seems that people are far too keen on oversimplifications. Whether it be on a specific issue, like seeking a comprehensible trigger for a school shooting, or on a more general topic like dismissing those on benefits as skivers (or, in the interests of impartiality, dismissing the wealthiest in society as "the 1%"), we like to make sense of the world with explanations and categorisations that cannot do justice to reality.
Of course, it makes sense for us to do this. I don't know if I'm alone in being willing to confess that I rarely understand even my own motivations, but it's clear enough that across the world we often struggle to understand our closest friends and relations, never mind the vast majority of the other seven billion people in the world, or the still more complicated array of natural processes. In such a confusing and tumultuous world, any progress or decision depends on us finding shortcuts towards understanding.
It's clear, from the very very beginning, that literature and language have helped in this process. Foundational myths helped make sense of the most challenging natural phenomena, giving our ancestors a framework to understand what they were, where they came from and why they were here. Indeed even before that point the development of language marks the first step in our ordering of the universe - words work by designating multiple objects as being essentially the same - once you have a word for 'apple' you no longer have the daily challenge of understanding the round red thing in your hand which is slightly different to what you ate yesterday.