You could go even farther, and just provide a way to run some Lua code at startup, and provide Lua APIs to add hooks, handlers, or whatever else you wanted.
But while as a programmer that sounds fine to me, I suspect for the average user who just wants to add a few lines to tweak something, quite possibly copying the configuration from a web site or a book, it's easier if we provide a bit more of a framework for them. Of course, the two options aren't mutually exclusive.
