What? I don't think this is true at all. Plaintext data, email or not, can be protected with robust encryption. Your end security is the main consideration, but that has nothing to do with the protocol or content, really.
Companies could at least insist that intra-company email is encrypted, which would be a huge amount of their normal communications, and then extend that outside their boundaries with partners who also accept (say) S/MIME.
At present I sign my mails but like you have no clients who use encryption.
The core problem with widespread crypto use today is not encryption, it's trusted key exchange.
But as it happens, yes, I trust our crypto developers. They're much better at it than most of HN.
And the rest of the code is pretty shitty in places.