There are already scores of email clients with support for GPG, etc. However more and more people (probably an overwhelming majority nowadays) use webmail only. I suppose they're the intended target.

I myself plan to migrate all of my data to my own services at some point, I already moved away from DropBox to Nextcloud. That could be a good solution to move my family out of the evil gmail, for instance.

Now what I'd like to know is which is better of MailPile, RoundCube, Zimbra, and the many other webmails available...