Probably more due to the fact that browsers only support the 1999 XSLT 1.0, and no one has shown any interest in implementing XSLT 2.0 from 2001, or XSLT 3.0 from 2017. So there has been a sign of lack of desire since 2001 at minimum, likewise there is seemingly no attempt by anyone to document incompatibilities and push browsers to unify their incompatibilities like HTML, JS, and CSS.

The writing has been on the wall for a long while. Mozilla hasn't stepped up, Google hasn't stepped up, GNOME hasn't stepped up, Oracle hasn't stepped up, etc. Maybe its just a format that once anyone gets involved with, they no longer want to be involved with it any further.