I'm not entirely sure, something to do with XML not being human readable maybe. All I can really say is that I don't use XML most of the time is because I'm lazy, JSON.parse() is just too easy but I also don't know XML that well and I believe that is because the large majority of RESTful interface's I work with are JSON.
Though I would love to hear someone else's thoughts on why an XML resume hasn't gained critical mass.
The trick with XML is to learn XSLT. The trick with that is it's really a weird language that uses recursion and acts almost functional, but not. But if you learn that, you don't have to parse anything because you just "style" the xml.
Here's a silly playground I wrote to show my students XML.
Though I would love to hear someone else's thoughts on why an XML resume hasn't gained critical mass.