Why Hire an Editor?
A perfectly reasonable question, coming from a new writer. We editors don't come cheap: depending on the level of editing your manuscript requires, you can expect to pay $0.01–$0.05 per word for our counsel (as per the Editorial Freelancers Association), which can add up to thousands of dollars for a novel-length work. And a thorough edit can take weeks, drawing out the already lengthy process of publication. What makes us worth the time and money? What do we do for you? And specifically...
Why can't I run my final draft through spellcheck and call it done?
Because you can't rely on your word processor's spelling- and grammar-checks to catch all errors. Despite the vast strides artificial intelligence has made recently in understanding human language, it still takes a human's contextual awareness to reliably tell wrong from right in English prose. This goes double for situations like fictional dialogue, in which it's often stylistically right to be grammatically wrong, or when one's choice of words depends on meaning (that vs. which, for example, or one homophone vs. another). You might not notice such mistakes when looking over your work, but your readers will trip over them like rocks on a racetrack.
Not to mention that a good editor also brings subjective stylistic expertise to the table. Even if word processors can someday tell a grammatically correct sentence from an incorrect one with perfect accuracy (according to whatever bizarre mishmash of style rules their makers program them to follow), I don't expect them to be able to tell an elegant sentence from a dull one within my working lifetime. And I've got several decades left at this.
As the details, so the whole. If the first page of your novel is full of awkward phrasing, why would a reader trust you to shape a satisfactory plot? If your article is riddled with misused, misspelled, or missing words, why would a reader trust you to supply accurate information? They wouldn't. And with that trust goes their desire to keep reading—they'll move right on to the next search result or Goodreads recommendation.
Okay, so I need a human to review my writing. Why can't I do it myself?
Because you cannot edit your own work.
This isn't to say you shouldn't try. You can (and should) revise your drafts and smooth them out as best you can before sending them off to an editor. There's no need to pay us to fix mistakes you could have caught yourself. But ultimately, as the author of a piece, you are too intimately involved with it to see it as a reader would.
What do I mean by that? When reading your own work, you tend to see what you meant to say rather than what you actually said. In fiction, you know every detail of your characters and plot. In nonfiction, you've internalized the information you've drawn from your sources. But either way, your brain fills in whatever's missing on the page. Your readers, however, don't have that background information; they'll trip again over your omissions.
And there's another intimacy issue at hand: you're in love with your own work. As you should be—nothing less than love could keep you pushing on through a thorny, tangled plot or keep you up till dawn rewording your thesis statement to perfection. But the same love that gets you through the writing hobbles you at editing. Every paragraph seems relevant to you, every sentence seems quote-worthy, and every joke seems perfectly executed... but we both know that can't be true. Some are, for sure (and it's as much an editor's job to point out these successes as it is to harp on your failures), but no matter how good of a writer you are, many aren't. It takes an impartial eye to tell you where your manuscript works as-is, where it can be improved, and where, unfortunately, there's no fix but deletion. And if you're at all serious about publication, that eye had better be a professional's.
And don't forget the technical aspects of copyediting: checking the minutiae of grammar and usage and ensuring that a manuscript conforms to the appropriate style manual. As an author, it's not worth your time to do that yourself. Outsource it to the pros and get back to what you do best: writing.
Good editing is one of the few services that can make your work stand out from the crowd. As a writer, particularly an unknown one, that leg up is invaluable.