Il ne semble pas à proprement parler "défendre son bout de gras",
lisez l'article et ses commentaires, c'est très intéressant.
J'en extrais ceci :
The nature of the files means that writing a viewer for other platforms is non-trivial; while it's possible to extract plain text from it, the plain text won't be particularly useful or accurate (and the plaintext representation of the book is only a very very small part of the file).
et
The format itself isn't really intended to be convertible to begin with. It's really more of an image format than a text format.