If you were a really fundamentalist christian would you be limited to only using things that are mentioned in the genesis as being created by god. After all anything else could be the work of the devil and they couldn't be sure whether it was or not.
They just make it up as they go along, if something doesn't suit them it's the work of the devil and if it does then it's alright. Notice how their leaders use modern media technology to spread the word.
I shouldn't bother trying to understand them if I was you, and that goes for most religions to be honest, some good bits but mainly a right load of old tosh.