by Scott Rhoades
"That was when Angel Wells became a fiction writer, whether he knew it or not. That's when he learned how to make the make-believe matter to him more than real life mattered to him; that's when he learned how to paint a picture that was not real and never would be real, but in order to be believed at all--even on a sunny Indian summer day--it had to be better made and seem more real than real; it had to sound at least possible." --John Irving, The Cider House Rules
That pretty much says it all. We need to take the unreal and make it seem more possible than reality, more interesting and more important than reality, by making it matter more than real life.
If we fail, our story sounds unreal, fake, insubstantial, and not important enough for a reader to make the effort to become engrossed in our world. The story will be put down and won't be picked up again.
If we succeed, our false worlds enhance the reader's reality, and make real life more enjoyable for the time it takes to read. And if we succeed really well, the story lingers in the reader's mind, becomes a part of the reader, and enhances reality far longer than the time it takes to read.