The following diagram illustrates the dangers the typical Internet user is up against. Generally motivated by the thoughts of other people's money, hackers find little incentive when everyone can tell who they are.
Attacks through conventional email including ransomware assaults rely on IP spoofing to hide the hacker's identity. This is not possible here, whether symmetric or asymmetric encryption is involved, as the sending of any post/email requires two-way communication, thus requiring the originator's valid IP address to complete a transaction.
The recent WannaCry and Petya global malware were all circulated by phishing email.