The new KiCad file formats are all S-expression based[0], except for the project files which are JSON IIRC. I think it works pretty well for representing a tree of typed objects textually. They don't even have any LISP connections. Haven't seen S-expressions used anywhere else, though.

[0]: https://dev-docs.kicad.org/en/file-formats/sexpr-intro/

I’d speculate that human minds and memories work much better with associative structures rather than sequenced ones. JSON draws a clean separation between these two and as a result has clearer syntax for the former.

ie, the benefits of simplicity have a limit.