It’s probably because of the publisher’s stance toward eBooks in libraries via Overdrive.(Chart of authors and their publishers.)
If you’d like to see more downloadable eBooks available in libraries, please contact publishers who impose limitations on eBook downloads to libraries to give them your feedback.
These publishers have never allowed eBooks to be distributed to libraries via Overdrive.
75 Varick Street
New York, NY 10013
Simon & Schuster
1230 Avenue of the Americas
New York, NY 10020
Hachette no longer offers eBook titles to libraries via Overdrive.
Hachette Book Group
466 Lexington Avenue #131
New York, NY 10017
Penguin Group no longer offers eBook titles to libraries via Overdrive. Previously purchased titles may no longer be transfered wirelessly to devices like WiFi enabled Kindles.
375 Hudson Street
New York, NY 10014
A Harper Collins library eBook license expires after 26 checkouts (effectively giving popular titles a one-year shelf life).
10 East 53rd Street
New York, NY 10022
Brian.Murray@harpercollins.com (CEO of HarperCollins Publishers)
Some information in this post used courtesy of Sarah Houghton-Jan, blogger and director of the San Rafael Public Library (CA) from her February, 2012 blog entry.