If you happen across the site for a business called Engaged Metrics, you'll find a home page overflowing with words. Take a look at a screenshot. (Be prepared to scroll a lot.)
I counted on this page some two dozen headlines followed by blocks of copy. The page has a scrolling slideshow, a scrolling client list, blog post links, links to video, various call-to-action buttons, and so on. It's a lot to take in. Meanwhile, the text is filled with lengthy buzzwords like "invite broadcasting," "organizational trending," and "core competency benchmarking." Generalities such as "Since it's your name on the line, we know how crucial it is that your project goes smoothly" add to the verbosity.
This company conducts employee surveys for other companies, and although the home page has a lot to say, finding out exactly how Engaged Metrics helps clients would take some digging. If the page contained fewer sections and each section contained just a few relevant phrases, the answer might become clear.
By contrast, the homepage for Dropbox is a paragon of restraint. The benefit is stated in a mere three words: "Your stuff, anywhere." The number of sections beneath the fold is only four, not dozens.
Whether the Dropbox home page on top and below the fold (not shown here) is as effective as it could be is something that could be debated, but it certainly delivers on brevity.
On the surface, it may seem easy to keep things short and simple. After all, there's less to write. But as indicated in the epigraph above, short is difficult. For marketing, it's also more effective.
Concisely expressed ideas—those that manage to be short but complete—are easier for a reader to remember, which means the business can extend the time they have for a customer to take action. Even more important, concise ideas are easier to understand. People don't have to spend time and mental energy trying to figure out why a company's services might matter to them.