I'm curious: who else uses these? Can there be a bit of show of hands?Anyone who cares to write comprehensive/printable documentation besides man pages? People who want some equations and schematics in their paper without wasting 100MB for teTeX/texlive?
You have ignored the context of the question, which regards use of the documents in /usr/src/share/doc/{psd,smm,usd}.
So to be explicitly clear:
Who regularly uses the documents in /usr/src/share/doc/{psd,smm,usd}?