The problem with PGP, part 3
It is difficult already to help people understand and participate in the certification network that forms that backbone of OpenPGP’s so-called “web of trust” … OpenPGP is confusing, and it can be tricky to get it right … And this mistake is one of the thousand papercuts that inhibits the robust growth of the OpenPGP certification network.
In order to use encryption software correctly, you will need to spend a significant amount of time learning important encryption concepts like public keys, private keys, keyrings, etc.
Using public-key encryption takes a commitment to learning a lot of new skills and jargon. The widespread adoption of public-key encryption is a long way off, so it may seem like a lot of work for not much benefit.
— riseup.net, Message Security
A communication tool is only useful if everyone you want to talk to is willing and able to use it. If it’s hard to use, it’s not going to catch on.