Users of the Books app are not able to directly spot uncategorized books or pdf docs

What is the purpose of providing the possibility to give books/docs a category if one cannot know which books/docs are still uncategorized ? I

s it so hard to offer the possibility to list uncategorized books only ( or uncategorized pdf docs only ) rather than showing all the books / docs in the library ? Why such negligence ?

The lack of this feature seriously decreases the user friendliness of the Books app. Zillion of users have asked for this over the past decade or so (ibooks app included).

Yet, Apple keeps neglecting these requests as if the do not care. Why is that ? When will Apple finally complete this incomplete categories-functionality so that people can start using it efficiently and without frustration ?

[Re-Titled by Moderator]