Why aren’t there more new releases available in e-book format?

Licensing terms of e-books to libraries vary among publishers. Many of the larger publishers impose strict limitations on the types of material libraries can purchase through their e-book vendors. 

The big 6 publishers became the big 5 on July 1 when Penguin merged with Random House. The publishers are:  Hachette, HarperCollins, Macmillan, Penguin Random House and Simon & Schuster.
These publishers each have different approaches to selling e-book titles to libraries and impose different conditions. Many smaller publishers, on the other hand, are content to sell their e-books to libraries.
Some of the restrictions imposed by the larger publishers include a substantial increase in the price of an e-book for a library compared to the price of the same book to the consumer and loan limits on titles. i.e., a title can be loaned 26 times and then it will be withdrawn from the collection.
The Australian Library and Information Association is actively pursuing a viable solution for all concerned – libraries, publishers, authors.
Their most recent issues paper can be accessed here.
IFLA (International Federation of Library Associations and Institutions) advocates for all libraries world-wide. They are working at an international level with WIPO (World Intellectual Property Organisation) on copyright and exceptions.
For information about IFLA’s e-lending principles, please visit this link.