According to Steven Pinker in “The Sense of Style”.
It ensures that writers will get their messages across.
Style earns trust. If readers can see that a writer cares about consistency and accuracy in her prose, they will be reassured that the writer cares about those virtues in conduct they cannot see as easily. Here is how one technology executive explains why he rejects job applications filled with errors of grammar and punctuation: “If it takes someone more than 20 years to notice how to properly use it’s, then that’s not a learning curve I’m comfortable with.”
Style, not least, adds beauty to the world. To a literate reader, a crisp sentence, an arresting metaphor, a witty aside, an elegant turn of phrase are among life’s greatest pleasures. And as we shall see in the first chapter, this thoroughly impractical virtue of good writing is where the practical effort of mastering good writing must begin.