An XML-based format has the advantage of being "out of the box"

Source: google search

The new formats improve file and data management, data recovery, and interoperability with line-of-business systems. They extend what is possible with the binary files of earlier versions. Any application that supports XML can access and work with data in the new file format. The application does not need to be part of the Microsoft Office system or even a Microsoft product. Users can also use standard transformations to extract or repurpose the data. In addition, security concerns are drastically reduced because the information is stored in XML, which is essentially plain text. Thus, the data can pass through corporate firewalls without hindrance.