[rhaps0dy]

>But if you already have a secure channel - what's the use case?

You can use Whatsapp, or some other E2E-encrypted service that is easy to use, and then transmit the sensitive data over encrypted email, which is more convenient for long-form text.

[dkopi]

Personally, I find the Whatsapp web version pretty convenient for long-form text

[jsingleton]

For text yes, but not so much for sending attachments like documents or other arbitrary files.