Because they're too complicated! If I want to get started with them, or extend them, there's a large learning curve.

For example, take a look at https://github.com/lakshmivyas/hyde/blob/master/hydeengine/f... or https://github.com/borismus/lightning/blob/master/lightning

What does all of that stuff do? Why does lightning need YAML and pickle? Why does hyde need to mirror the entirety of python's os module, including os.walk, for both Files and Folders?

Now compare that to my version: https://bitbucket.org/anthonyb/shithead/src/8a8e5787cf6a/blo... , which is essentially the entire engine, file system handling and building code.