How do I modestly cover myself?

In March 2013 I wrote about cover letters and how to impress with a really good one. On re-reading, I notice that two years ago I was fantasizing about Ryan Gosling. Still am. And he still hasn’t called.
The thought occurred that in the previous blog article I didn’t answer the initial question, “Why do I send a cover letter?” I could therefore usefully have called this blog “WHY do I modestly cover myself?” but I didn’t think that was as amusing a heading as the one I have chosen. Either way, you knew immediately from the title that I was going to write about cover letters, there can’t have been any confusion with anything else?
What is the point in writing cover letters?
Everyone does them, so you’d have to have a jolly good reason for just sending your resume out there with nothing to explain it. They might even think you’d forgotten to include it.
Your resume is perfect for that particular job and stands by itself without need of any extraneous help; in fact, Human Resources will be oohing and aahing over it and passing it round the department to marvel at its fabulosity? Possible but not probable…
The cover letter gives you a chance to highlight from the resume the two or three main components that are particularly relevant for the job – ideally in the form of achievements. Achievements let you mention numbers. Men, mathematicians of both sexes, and Human Resources just love their numbers. In HR’s case, they want to know how you quantitatively increased the good stuff, and decreased the bad stuff.
You can show off your writing skills. Resumes have to be well-written, but they should be written succinctly, in phrases. More in the less-is-more, Hemingway-style brevity, less in the you-can’t-pay-me-to-read-all-this-through-to-the-end Henry James-style denseness. It was popular in the 80s, but so was Bruce Willis. These days resumes have to be bullet-pointed brief. I digress à la Henry James. Cover letters give you the opportunity, more than a resume will, to showcase your writing ability, and let the world know you can write whole grammatical, error-free sentences with subjects and predicates that would make your English teacher beam with pride.
A resume is about YOU, after all, but a cover letter can allow you to relate what you’ve done/achieved to the company’s goals, culture, mission. The company, and the specific job, is all about THEM, let us never forget, so a little buttering-up to highlight that fact won’t go wrong.