Why and How I Write Scientific Documents in Plain Text sets out some good reasons for ditch the conventional word processor in favour of a text editor

To write something in Word, I have to actively not look at all of the formatting options. Think about it this way. Because we read from the top to the bottom of a page, our eyes naturally gravitate to the top. But in Word, the top quarter of the screen consists of buttons that, while writing, you have to ignore. To me, that seems like unneeded mental effort.

Today, I favor a distraction-free interface — something you can’t really get using a word processor. (WYSIWYG formatting requires point-and-click menus.) To get distraction-free writing, I use an old-fashioned text editor. There are hundreds of different editors, but I use gedit. Like modern internet browsers, gedit’s top panel is bare bones. The lack of distracting buttons puts the focus on your writing.

It's a long while since I've written anything like a scientific paper, but the reasoning used here makes sense for any sort of writing. Using plain text lets you focus on your words, not how they look.