why cissp says this about PGP/GnuPG?

[Beff Con]

Hi, list!

    I'm reading a book named "ALL-in-One CISSP Certification Exam
Guide" by Shon Harris, 3ed.  And in "Chapter 8 Cryptography", I came
across a paragraph like this:

"How strong of a protection mechanism is required depends on the
sensitivity of the data being protected. It is not necessary to
encrypt information about a friend's Saturday barbeque with a
top-secret encryption algorithm; conversely, it is not a good idea to
send intercepted spy information using PGP. Each type of encryption
mechanism has its place and purpose."

   I wonder why PGP is not good enough to encrypt spy information?

   thanks in advance!

 Beff