XML.com FAQs > A. General questions
Question:  A.9 Why do we need all this SGML stuff? Why not just use Word or Notes?

Information on a network which connects many different types of computer has to be usable on all of them. Public information cannot afford to be restricted to one make or model or manufacturer, or to cede control of its data format to private hands. It is also helpful for such information to be in a form that can be reused in many different ways, as this can minimize wasted time and effort. Proprietary data formats, no matter how well documented or publicized, are simply not an option: their control still resides in private hands and they can be changed or withdrawn arbitrarily without notice.

SGML is the international standard for defining this kind of application, but those who need an alternative based on different software for other purposes are entirely free to implement similar services using such a system, especially if they are for private use.

This FAQ is from The XML FAQ, maintained by Peter Flynn