Publishers put ridiculous rules in place for digital content. Libraries typically need to pay the full cover price for an ebook and it expires after 1-2 years. So not only can libraries not receive donations of used ebooks like they can physical books, they are also restricted by the limited life span. Sure, physical books experience wear and tear, but that’s built up through use. A less popular book could sit on the shelf for a long time and not degrade substantially, but an ebook could go without being checked out once and it will still expire.
If I’m buying an ebook from a DRM enabled bookstore, there is no reason why I should not be able to sell the book or donate it to a library when I’m done.