@desea If you wanted to be charitable you could say its just to fill up "yet not filled with books"-space so it looks better (maybe).
I do have bookshelfs here and they do be filled with books (partly). Though most are books I already and I am not one to read books multiple times.
Certainly has a different vibe than a digital collection.
If you want the less favorable outcome. Fuck these people only having fake books. Not real bookworms!