Some instructors want to provide a file to just some students. Being able to restrict access of a specific file to just some users could be implemented.
Could you explain a use case for this? One where sending the file through a conversations' post would not be sufficient.
The reasons are the same for why an instructor may want to restrict a page or announcement to just some students. There should be a way for course materials to be housed in the course they are for. If the materials are sent via Conversation, that places some course content outside of the course propper. I would agree best practice would likely include sending the Conversation, but it seems to me to be a shabby workaround.
Retrieving data ...