I think it's a mix of the convenience factor being low enough* that it mostly appeal to technical people, and the complexity factor also being low enough that a

I think it's a mix of the convenience factor being low enough* that it mostly appeal to technical people, and the complexity factor also being low enough that a lot of said technical people think they can do it in a week-end (I did my first prototype in 2 or 3 evenings) or two. You can start simple with MAKEFILEs, perl scripts, pandoc and other basic/builtin unix scripts etc... and go up to build a full SSG site in Node or Ruby / Python etc... with a million dependencies if you wish to. *: every time you want to publish something you have to run a command , wait and push the output to a webhost configured properly, as opposed to installing something once and writing in a webform and your words appear on the site.