I remember David Weinberger once saying that "documents are dead". Would that things were that simple!
I watch people in business struggling with the persistent idea that documents are how we convey information. We still think of them as real things, formatted for reading on paper, stored in pretend folders, lying on pretend desktops.
Yes there is some stuff that still gets printed off, but nowadays is it more likely that the same content can be presented as a web site, shared as an editable Google Doc, or read as PDFs, ePub, and on umpteen different devices with different demands and formats. The result is a stressful mess for many people in business who write in one format then publish in another, mangle documents into PDFs – and don't even start me on forms written in Word that break when you try to complete them. There is also the ongoing issue of incompatible legacy formats which only seems to get worse.
The combination of these issues is why I do all of my writing in plain text. The tools are simple and lightweight, I don't get tempted to faff around with fonts and formatting instead of getting the ideas down "on paper", and I know I will always be able to open any text file on any computer.
Only at the very end do I think of formatting and where the text will end up. I am writing this, as I do all of my writing on anything but long form stuff, in Drafts, a wonderful iOS app that allows me to "send" the finished text to umpteen other apps in umpteen formats – and only once the writing is finished.