In some XML files, there are values that require additional parsing rather than using XML to structure that data. I suppose it's because something like

  <values>1,2,3</values>

is more compact and more friendly for human editing than

  <values><value>1</value><value>2</value><value>3</value><values>

The worst example is SVG. SVG seems designed to make the format compact, using many single letter elements, but it also had to be XML, which is not compact. It also has data, such as path and transform values that have their own syntax. If that data were instead structured with XML, the size of the SVG document would explode. My conclusion is that XML is being shoehorned into places where it's just awkward. Probably because there are lots of XML tools and expertise, and no obvious alternative.