mso489:
I think you've nailed the reason that virtually every book on pipes and pipe smoking written since 1980 has either been self-published or published by tiny, tiny specialized publishers that may or may not pay their authors anything.
That said, I think there have been some wonderfully enjoyable books on pipes and pipe tobacco published in the last 50 or so years. I enjoy Carl Weber's books immensely. Carl Ehwa's is a classic. And I think Rick Hacker has also done much to make pipe smoking interesting and appealing to new generations. But, frankly, unless you're going to get into some specific areas of the hobby, there's not much more to say at this point that hasn't already been said -- and many times. I think that helps to explain the popularity of Rick Newcombe's books, which I found really unappealing to read. They're the books Hacker would now be writing if he were still interested in pipes: Pipe smoking as status symbol. (Hacker didn't start out with that tone; it developed as he became the "expert" spokesperson about pipes and, then, cigars in the late-1980s and 1990s. Then it became more about the Cigar Aficionado "lifestyle" than pipe smoking.)
I have read that prior to 1800, English-language publications about tobacco and smoking were second in number only to English-language publications about religion and the Bible. Pamphlets, broadsheets, flyers, books, etc. were being produced -- and consumed -- at a furious rate. Things slowed down as smoking went from being a new and wonderful/horrendous thing (depending on your point of view) to becoming a commonplace of daily life. And the late 1700s also saw the creation of the novel, which led to an enormous surge of fiction in the 1800s. It's interesting that, out of all that writing, the pipe smoking writing that survives today -- or at least the writing that continues to be read -- is poetry (Pipe and Pouch) and fiction (My Lady Nicotine).
Bob