Zimmermann said that the main reason he wasn’t using PGP is that he couldn’t run the necessary encryption software on his MacBook, since Symantec bought PGP in 2010 to incorporate the technology into its own products.
Zimmerman also said there was “no version of PGP ever ran on an iOS device.”
(It is worth noting that you can encrypt emails and files on Macs using GPG Tools, which served as PGP’s de facto replacement after the Symantec acquisition — if you like to inflict that kind of pain on yourself.)