I live in the Cleveland area. I thought I'd share some searches I ran today in the online catalogs for CLEVNET, a consortium of northern Ohio libraries that includes 35 public libraries including the Cleveland Public Library, and for Cuyahoga County Public Library, which serves metropolitan Cleveland and has 28 branches.
Number of Robert Anton Wilson works listed in the CLEVNET catalog: 21. Number of Robert Shea items: five, but just three titles.
Number of Robert Anton Wilson books held by the Cuyahoga County Public Library: None. Number of Robert Shea books: None.
Libraries have a limited amount of shelf space. They constantly buy new books, which means that old ones have to be culled from the collection and gotten rid of in some way (sales by library volunteer groups, sealed in boxes and thrown away, etc.). The easiest, most logical way to cull the collection is to get rid of the books that haven't been checked out in awhile. If you want your favorite writer's books to remain available in public libraries, check them out.