You should want to sing “the end” from the rooftops, not vomit in the sand between the back of a portaloo and someone’s million-dollar Cape Cod-style McMansion.
The why factor tells reader things about your characters. Readers learn who people, and they connect more deeply with the story, such as in “The Gift of the Magi” when writers show instead of tell.
Why does a good book cover matter? The cover is an important marketing tool for your book, which is why you should leave book cover design to the pros.