On the face of it, it seems a straightforward conclusion. If a book provides no additional benefit to it's reader, and the needs of that reader can be met equally and more efficiently with another commensurate medium, what purpose does such a book serve? Medical journals are moving faster than ever into the digital age; whilst some preserve printed copies for monthly subscribers, most at least publish a digital equivalent and, increasingly, journals are moving to a digital-only subscription model.
It's not quite a done fight just yet, however. There is a particular aesthetic benefit that conveys an advantage to printed books; owners become more attached to printed books than they do to ebooks. Heritage and style are less emphatic read as a PDF compared with the distinct smelling, aging books.
Does that negate from the fact that ebooks are cheaper, more accessible and transportable than their printed versions? Not at all, but for many people those attributes are not essential but optional.