Just to clarify one or two things…
Simply explained, the reading apps grab their metadata from a file inside the ePub; the OPF file. If this file is not correctly filled, the app will display that incorrect metadata. So it’s really the fault of the people that made the ePub. For example, for the book where the ePub says “Philosophy, Theology.” a reading app will put it in the following category “Philosophy, Theology.” As simple as that. If the publisher inputs “hi, test” then that will be the category.
The other thing you need to be aware of is that publishers, when sending a book to a retailer like Apple, Google or Amazon, also send a metadata file alongside the ePub file, usually in an XML format called ONIX. This ONIX will contain the categories of the book (BISAC system for the USA, BIC for spain, CLIL for France, etc.). So usually the web stores (iBooks Store, Google Play books, Amazon website) use these categories to sort the books online, and not the information inside the OPF.
I do agree 100% with you, publishers are not still as aware as they should be about the importance of metadata. I think Apple, Google and Amazon are, but they have to work with whatever the publishers send.
