Not really, it's because org-mode is completely almost unusable outside of Emacs. Unlike Markdown, it looks terrible as truly plain text. And Emacs, while great in so many ways, is is an esoteric paradigm (same with vim, but many of us are hooked on it anyway).

Ubiquitous keyboard layouts, text editing and markup paradigms are all due for a massive shake up, but agreed they have a lot to learn from the Emacs stuff.

Probably because org-mode has a horrible name.

piggy backing on this comment to mention that github can render .org files :).