XSLT is a declarative language for transforming XML to other formats. XML is a pretty poor solution for configuration files (which is what everybody seemed to use it for back in the day) but works great for, you guessed it, marking up documents. If you have an XML schema for representing documents semantically you can then write an XSLT that quickly and efficiently converts it to, say, XHTML. This way you can work in a nice intermediate representation rich with meaning and specify the presentation as a function thereof.

It's not particularly sexy technology but it works well when used judiciously. Part of me wonders if XML will make some bizarre comeback in the era of LLMs for training data annotation or something similarly niche.

Ok, but my question stands. What value does this provide society?