Markdown doesn’t do most of what those formats do. You can’t set margins. You can’t do columns. You can’t embed a pivot table or track changes or add a watermark that says DRAFT across every page in 45-degree gray Calibri. Markdown doesn’t even have a native way to change the font color.
And none of that mattered, because it turns out most writing isn’t about any of those things. Most writing is about getting words down in a structure that makes sense, and then getting those words in front of other people. Markdown does that with less friction than anything else ever created. You can learn it in ten minutes, write it in any text editor on any device, read the source file without rendering it, diff it in version control, and convert it to virtually any output format.
Markdown Ate The World is a nice and well-informed article. I appreciated the early brief history of word-processing file formats. I didn’t know, for example, that .docx is just a zipped XML file. Oh, and I vividly remember the old times, when .doc files were as fragile as candles in the wind.