There are literally dozens of examples of text-based markup tools that are cross-platform, version-controllable, and can be rendered in a terminal if you're into that, and which don't require me to waste time drawing ridiculous ASCII art borders to denote logical relations.
2. Version control for binaries sucks.
3. Graphical tools can be very awkward when aligning stuff. MS Word, for example, is a pain for making diagrams in.