One of the key insights of LISP is that s-expressions are a simple, universal format. Yes, they can be used for code, but they can also be used for static configuration data. In fact, LISP originally used s-expressions solely for data; code was meant to be written with m-expressions ( http://en.wikipedia.org/wiki/M-expression ). Once `eval` was implemented, s-expressions could be used for code and data, so the idea of m-expressions was abandoned.

> A configuration language is for storing state - key/value pairs or simple structures of primitive types, nothing more (or as little more as necessary), nothing less.

The trouble with "universal" formats like this is that there's no universal agreement on what's a "primitive type" (what happens when I write `0.1`? Are booleans primitive, or should we use `0` and `1`?) and what's a "simple structure" (can I make a circular list?). That in itself wouldn't be too bad, but these languages tend to hard-code special syntax to particular types and structures, so any types or structures we may want to add must either be second-class citizens, or would require hacking the parser.