A .docx file is a zip of XML. Open it in Notepad and you’ll see what your document looks like to a machine: namespaces, tag soup, paragraph properties, run properties, embedded font codepoints. None of it is readable. None of it is portable. Open it in Word 2003 and half of it breaks. Open it in twenty years and you’re betting that Microsoft still ships an XML parser.
A Markdown file is text. Open it in Notepad, BBEdit, Vim, less, cat, head, any text editor written in the last forty years. Open it in twenty years and it still works because text is the part of computing that doesn’t change.
Every document you write in sweetdocs is a Markdown file you own. Export drops it on your disk as plain text. The format isn’t a sweetdocs feature. It’s an open spec, used by every static site generator, every README on GitHub, every Stack Overflow answer. Your document survives us. That’s the point.