Why?
To use existing XML 1.0 tools on data that comes in as JSON. It may be somewhat problematic that it doesn't actually support all JSON, because the characters that are permitted (even with escapes) in XML 1.0 text do not include all characters that can appear in JSON values, so if you use it on legal JSON that isn't constrained to be XML 1.0 compatible, it will do something wrong (the docs aren't clear on whether it w…
Do you have an example of this? I'm curious what character you could have in JSON that you couldn't represent in XML using the '&#' syntax.
Edit: To answer my own question, backspace is an example of such a character.  is not valid XML.