Preserving the Library in the Digital Age

In a recent issue of The Readex Report, Benjamin L. Carp, Assistant Professor of History at Tufts University gives us five reasons why, despite his love for digitized resources, he still loves and wants libraries:

1. Rare or unique archival materials
2. Browsable stacks
3. Knowledgeable, experienced librarians
4. The buzz of studious patrons
5. All the usual reasons to love libraries

Completely unrelated, why is it knowledgeable but not browseable?