Laravel: Use case for File Visibility?

I am using Laravel with a local filesystem as storage driver.

I have understood that I can save files in the storage/public folder to make them accessible through http://ift.tt/2hBu7MT. I have also understood that I can make images accessible only for authenticated users like explained here.

What I have not understood it the File Visibility property. If files are public depending on the folder that I stored them, why would I need to declare them additionally as private or public? Could anyone give a use case where this would be necessary?

via Chebli Mohamed