But I do question why lib and not something in app is the common suggestion for classes/modules who do not fall into the default set of folders (models, controllers, jobs, etc). Is it just because it's what we've been doing for so long? To me feels like we're trying to shoehorn the lib folder into further being a kitchen sink (now holding rake tasks and miscellaneous classes), rather than just saying "your Ruby classes/modules go somewhere in app because they're application code".