Of all the people I know, librarians are the least likely to throw away information. Catalogs are information. Catalogs tell the librarian what's newly published. What information is currently available to their patrons. Librarians not only don't throw away catalogs, they circulate them to other librarians, file them for reference, and refer to them for up to three years after the catalog is mailed.
Librarians are serious buyers.
Nothing could be further than the truth. Librarians are consumers just like everyone else. One publisher I worked with had a lot of microfilm locked in their vault that had never sold one copy in 3 years. Within a year, this one catalog generated over a million dollars from the library market. Librarians won't buy a book that hasn't been reviewed.