Man I’ve I never noticed the class ring before, but it’s a perfect detail.

the os doesn’t create the files, the application does

When an application wants to create a file, who does it ask for permission? Who facilitates finding a spot on the disk for the new files to go?

Frankly I can’t speak to the overhead for managing it but the OS is aware and could very much keep track of which applications own what. As for shared directories if they know the specific app owner obviously just remove files from app A but keep the directory if app B also uses it.

As for configuration files and save data, these are generally located in consistent places but ultimately that’s going to be a responsibility of the app developer to keep with standards for where those config files go so they can persist through reinstalls.

‘Do you want to delete this application completely, or would you like to keep configuration files and save data?’

But Apple doesn’t really care, they want everything to feel seamless and look pretty. Actual functionality is a second thought.

But if it was a default functionality from Apple, presumably apps would be packaged, installed, and run in such a way that the OS is aware of what files it’s creating and use that context to clean up after themselves properly when uninstalled.