Docx doesn't play nice. At a time when they could have contributed to open standards such as odt, and as projects like Openoffice were getting a handle on the doc format, Microsoft rolled out DocX to stir the pot.

DocX has some silly compression built in. Microsoft pitched this to some large customers on the basis of all the disk space it would save. How large are text documents? Are they really in need of compression? Only he most massive of corporations see any appreciable reduction in storage needs over the old doc format.