Some books both in local stores and ordered online have dark smudges on them.
Here are a few examples:


One was ordered from global seller, another from a local auction site. Both new unused books.
About 1/3 of books I bought since 2017 from the global seller arrive dirty.
What's going on? Has anyone else encountered the phenomena?
I have a theory that price wars between store chains and pressure for higher store discounts has led to collapse of quality of shipping and storage which resulted in books getting regularly damaged or stored in dirty conditions.