I agree with the author that SSGs are tools written by developers for their own use. But what's great about the file-based, command-line-driven interface is that it's possible to hook the input side up to some more machinery if you want a GUI CMS.

I work for Forestry.io, and our product is a CMS that aims to ease the pain of non-developers managing content for static sites. We are committed to bridging the gap between copywriters and developers. I am a big believer in the potential for static sites to transform the web, but I realize there is a lot of ground left to cover.