What is ODT?
What LibreOffice, OpenOffice and Google Docs save a document as, and the ISO-standard counterpart to .docx. Inside it is a zip of XML, which is the reason a table drawn in one can be read back out at all. It is a page format first - paragraphs, page breaks, headers, footnotes - so the only part of it that is data is a table someone drew on the page.
What is Markdown?
Plain text with just enough punctuation to imply formatting, which is why it ended up as the default for READMEs, issues, wikis and notes. Its tables are the awkward part - a pipe-and-dash grid that's readable enough written by hand and tedious to maintain by hand.