The reason is obvious: to prove that we can, that we can ride this kind of roller coaster. To exert a remarkable control over the images which our eyes look at day after day and we find a way to write what we see. We write it in all five senses and in colors. We rummage in our heads for words to describe all of it. The possibilities are endless.
Imagery helps readers understand the fictive world, and, to create mood. Here is an example of that from the opening of my novel, Blow Forward.
“Lizzie’s gut clenched as she headed for the entrance, coffee mug in hand. She checked off a mental checklist of responses, the ones she always used after dispatchers gave her a hard time when first meeting her. She shoved her hand in her pocket. The feel of the mace canister—its cool, dispassionate solidity—comforted her. Some of the tension of having to face the outside world seemed to dissolve.”
This particular imagery creates a mood of foreboding. Lizzie’s “gut clenched”. We immediately know that something is wrong. The story further goes to tell that she checks for the mace canister in her pocket. Why does she feel that she needs to protect herself? It is a good example of imagery that the reader is able to immediately pictures the kind of mood and setting in which the scene may take place.
Here is another example from Shakespeare’s famous play He used a type of opening to elicit a response of looming danger from the reader when the three witches in the beginning speak of the, “thunder, lightning [and] rain” and the “fog and filthy air.”
Ah, but the act of writing and then presenting the story to the world is a very peculiar sort of challenge, indeed. This kind of world building becomes the reader’s property with which to form all sorts of interpretations and analysis. In short, your work may be subject to scrutiny -- public lynching or praise. But you’re willing to take the chance.