Perfect is the enemy of good. Mass adoption of PGP would made the work of hackers and spy agencies orders of magnitude harder. Moxie writes from a personal per

Perfect is the enemy of good. Mass adoption of PGP would made the work of hackers and spy agencies orders of magnitude harder. Moxie writes from a personal perspective and you'll notice he never claims to have something better in hand. His Signal still lacks utterly basic functionality provided by PGP, most important among them the ability to transmit arbitrary attachments (Signal only supports an undisclosed list of media attachments) but also including the ability to retain your messages long term in a particular location. Meanwhile, many of the tradeoffs made to make Signal easy could be made using PGP: Automatic generation of keys; centralized key repo; centralized mapping of keys to contact points (email/phone); trust by default.