Because PGP was software, not documentation. Such a clause would be prefectly ok for free documentation.
Again: Documentation is part of the software.
It _can_ be part of the program, but for Emacs and the GNU C library and other works, this isn't the case. They are two seperatly licensed entities. PGP as a whole was licensed under a non-free software license.
You can ask the FSF to make a execption for examples. This makes sense, and I doubt anyone would object.
I tried to tell that there are 48 lines of actual description (a work) plus some more lines with examples.
What was the result?
Cheers.