Years ago, I was asked to co-author a book. I was working as a computer programmer. I was known a bit for my skill. I thought, "Gee this is great!" Then the "contract" arrived. Who the heck wants exclusive movie rights to a book about the latest version of a compiler? Talk about stupid things to haggle over.
In the end, the publisher rejected the manuscript we submitted. The reason, the book was not thick enough. Their thinking was that thicker books are more noticeable on retail shelves and so sell more. My co-author wanted to "shop it around". He never did find a taker. 6 months later the software house released an updated version and the manuscript was out of date.
I know it is not the same, but I have found that even a low traffic website will generate in excess of 11,000 hits a month. While I could load it with banner ads to make a few pennies, it would not be the website I would want to visit. I do get the "it's on the web, it is public domain" clowns who complain about watermarks. It is simply the reality of our changing world.
Pete