It didn't survive because HTML5 came along with very well defined and strict parsing rules. You don't need closing tags for a specification to be strict. As lo

It didn't survive because HTML5 came along with very well defined and strict parsing rules. You don't need closing tags for a specification to be strict. As long as you define the parsing rules rigorously as HTML5 does, there is little benefit in XML compliance and there is in a well defined non-XML standard as it is mostly backwards compatible.