"PGP is too tricky for many."
Email itself would be too tricky if you had to connect to the server with telnet and type in all the responses by hand. All that is wrapped up in the client's standard behaviour. HTTPS would be too tricky if the user had to vet the certificates themselves but the client does that.
PGP is too tricky because it's not built into the standard as a basic element, in particular it needs a PKI which isn't provided for in the current email architecture. If we moved to a new standard which included the handling of private keys as part of the provision of a server the whole thing would just disappear into the background for most users.