NPR did a good and brief piece on digital lending economics which also talks about how those economics are different from physical lending. Libraries license materials, and the license for a physical book will typically last as long as that book can be circulated(basically until it falls apart).
I've started going to the library more often(and using Libby for e-reading), they might not have the exact book I want, but there is always something I am interested in there.
> Libraries license materials, and the license for a physical book will typically last as long as that book can be circulated(basically until it falls apart).
Libraries buy books, which are then covered by first sale doctrine. When a library book falls apart, the library may rebind it and continue lending it.