It'll be interesting to see whether companies start to shift to using encrypted email over the next few decades - it's not that hard to set up if you know the counterparty will be using encryption of the same kind, and if it's not a service bought in from an external company you can fairly sure it is secure.

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.