WYSIWYG: What you see is what you get.
By default, WordPress dumps pretty much everything but your title into that big body field—though most think tanks are getting better about that. It’s basically a document for the web. You can even get a plugin to make your WordPress WYSIWYG editor look like an old version of Microsoft Word. (Don't do that.)
Authors want control. They want to be able to insert charts and photos and tables in specific places. They want to control the order in which readers see content. Control is why so many authors—particularly those who specialize in longform content—are devoted to their PDFs. Control is why we have body fields with [WYSIWYG(WYSIWYG (defined))] editors. And control can give us beautifully art-directed, prize-winning pieces like the New York Times’ Snow Fall.
So I worked with two of my colleagues to re-engineer the entire FactCheck.org website. There was some structure (custom post metadata—ugh). But there was also a lot of hacky code and a big fat WYSIWYG editor.
We still write content as if it will go into pages and chapters. We build some internal navigation to guide people to different chapters. We build sophisticated web publishing tools—then saddle them with WYSIWYG editors lifted from word processing programs that are meant to spit out pieces of paper. We drop nice, linear copy into boxes labeled “body,” then demand live previews or inline editing so that we can see how our page is typeset.