For the books that are too tall for the shelves, why are they shelved sideways with the spines facing down instead of up?

For the books that are too tall for the shelves, why are they shelved sideways with the spines facing down instead of up? Wouldn't it make more sense for the spines to face up so people can read the call #'s without pulling the book out? If I am missing something please let me know.
For the books that are too tall for the shelves, why are they shelved sideways with the spines facing down instead of up? Wouldn’t it make more sense for the spines to face up so people can read the call #’s without pulling the book out? If I am missing something please let me know.

This is done for preservation purposes. Book covers tend to be slightly larger than book pages. Therefore, shelving these books with their spines facing up would damage the binding. We are currently conducting a library-wide collection maintenance project that includes the expansion of the oversize section to accommodate items that are currently shelved sideways.