I know the lib/ directory can be added to the autoload_paths and eager_load_paths quite easily. But I don't quite understand why files in lib/ are not autoloaded or eager loaded by default?
I can't find a simple answer anywhere unfortunately so I'd really appreciate if someone could explain this to me simply!
Because there is no Rails convention for putting files in lib that require autoloading. lib is for rake/thor tasks which reside lib/tasks and little else.
Your application-specific files should go in app. If you find yourself thinking of putting something in lib, it probably belongs somewhere in app, or in a Gem.