FYI, a Common Lisp book nearly made it out of the gate a couple of years ago, Nick Levine's 'Lisp Out of the Box'. The contents of it are available under a Creative Commons license:
It seems to be a strong recommendation rather than a hard rule, though. Clojure is worthy of an exception in my opinion.
I've been dabbling in Lisp (read Land of Lisp and am going through PCL) and eventually I'd like to create my own text-based game using common lisp. However, I am indeed wondering if/how it would make sense to use it at work.
»We're NOT looking for: (...) Books on topics that have dismal sales despite quality books being available. (If you're addressing a topic where good books have sold dismally in the past (for instance, LISP, LaTeX, or Web-based training), you have a much higher threshold to clear with your proposal. Convince us why there is a revival of interest in your topic, or why your approach to a deadly topic will provoke interest nonetheless.)« (from http://oreilly.com/oreilly/author/writeforus_1101.html)
However, in 2009 an O'Reilly editor wrote: »I think there's reason to believe that's changing, particularly with the right book; LISP awareness has been growing for the past couple of years. Our Haskell book has outsold expectations; Erlang has obviously made a comeback; so there has been a relatively recent shift in the language map.« (from http://lisp-book.org/talks/eclm-2011-10-23/plan.txt)
Also typical Lisp hacker won't buy a slightly edited and printed version of the HyperSpec or a printed version of the SBCL manual.
Add to that that Lisp made a deep dive after the AI winter and that they were sure to not sell enough copies. At that time it was also a good idea not to be connected to Lisp.
Plus, I guess they did not like Lisp. 'Clojure' has the 'advantage' not to use 'Lisp' in its name.