Here’s the way traditional commercial book publishing has worked for a long, long time – they take a financial risk to find unknown readers for your book. Reaching an unknown reader is risky though.
Publishers and bookstores do not really know the identity of readers. They are hoping the unknown reader will find the right book on the right day. They will confess that they are quite often surprised at the failure or success of publishing projects.
Because they take this risk with the traditional publishing model, the publisher and the bookstore keep more than 85% of what a reader will pay for a book. It is also why most writers do not have access to the process.