Archivists typically don't like destroying a work when preserving it. Scanning a book also only gives you an optical image. In some cases, like medieval manuscr

Archivists typically don't like destroying a work when preserving it. Scanning a book also only gives you an optical image. In some cases, like medieval manuscripts, the pages may have been erased and written over. If we simply scan the book and destroy the physical copy, we've lost that evidence. But again, for cheap mass-market works, most archivists probably won't care about destroying one copy out of a million to preserve the work. It's really only a problem for very old and very rare works