There are a lot of different implementations out there at the moment. A common extension for XML will benefit enterprises because they'll be able to count on this API to be stable and secure, and they needn't be concerned about incompatibilities with each vendor using a proprietary parser.
Quotes about parser (2 Quotes)
Writing a really general parser is a major but different undertaking, by far the hardest points being sensitivity to context and resolution of ambiguity.