the issue is as soon as you introduce a scripting language in a solution, people will write monstrosities with that. A configuration format guarantees that configuration will stay simple and "readable". I agree that LISP should be used more often though.
I have now seen enough deployments of puppet, salt, ansible, etc. to last me a lifetime and then some. Trust me. People have managed to turn configuration formats into unreadable monstrosities as well. At least with a real programming language I would have sensible debugging capabilities and maybe some refactoring tools to help but with a half-baked YAML programming language I have no such recourse.
