The digital world is ephemeral.
Per that last example, consider that the "Nooked" War and Peace could be considered a "great typo" someday sought after by collectors - except that, being ephemera, the digital copy will either be lost or copies unverifiable due to ease of replication.
I certainly appreciate the benefits of e-books. At the same time, physical presence carries a lot of meaning beyond just content. Alas for those notable books lost in a sea of bits...
The book-equivalent of source code is the collection of discarded drafts and working notes of the author. These, too, are often lost, but that has little to do with whether they are digital or not.
It's expensive to properly store and maintain physical copies of things like books. I understand that archivists have some trepidation replacing a known system of storing physical books with a relatively unfamiliar and untested system of storing digital goods. But the bugs are already being worked out; if you want to make sure something lasts, make it digital and make sure lots of others can get to it.