Earlier quoted context omitted.
I use it extensively for managing the books on my devices (Kobo Libre, and my wife has an old Kindle).
What’s there to manage? They are files. Read a book, copy a new book over, delete old book. A file manager does all that, and is simpler and easier.
I do agree I could live without it but files tend to accumulate and putting books in collections help.
All of this would be much easier if the kobo was dumber and just created shelves/collections based on folders.