That might be a niche within a niche.

With the advent of Learn You a Haskell, Real World Haskell, Haskell Book...etc, I really feel it is a lot more popular now, but I don't have your experience to draw upon so maybe it is just cognitive dissonance on my part.

I doubt Paul Graham was into the theoretical programming scene in that era. He might have been aware of it, but I doubt it was as production worthy as Common Lisp and thus probably not worthy of his time.