[lathiat]

Before JSON and YAML, XML was all the rage in the sort of 2000-2005 era. Plenty of config files etc using it in the Linux desktop space.

Not sure if it’s related to this case or not but it was once much more popular even for sometimes human written files.

[dilyevsky]

Solaris descendants like SmartOS were also heavy on xml configs as I recall

[pjmlp]

Like all NeXTSTEP ones.