I'd say it's the difference between going to a cinema to see a movie, compared to watching one of those "behind-the-scenes" or "making-of" documentaries. The "general public" only want to see the final product, and sometimes the artist doesn't want their techniques known.
It's us nerds, geeks, students, gearheads, whatever, who want to know the process, the camera, lens, film, developer, paper, whatever. Sometimes so we can directly replicate the results, sometimes so we can learn a new technique, sometimes just out of GAS-based curiosity.
Maybe convince your favourite photographers to do a "making of" or "behind the scenes" book of their favourite / most well known photos? I don't think it would sell as well as their portfolio books, a small few of us would be interested but the general public just won't care enough to make it very profitable, unfortunately...