Using most current email client software, I can easily send you an email. But I can’t change it once it has been sent.
Alternatively, I can choose to do things in a much more formal way, sending you a link to a Web page or a Google doc. In that case I can continue to modify my message after the fact.
To me it feels as though we are being forced to one of two extremes, when there really should be something in between. Email clients should provide an easy way of creating a casual modifiable document just for the purposes of our email communication.
You and I would both understand that I am sending you a message that contains evolving content. You can then choose to reply with your own message which contains evolving content.
But we would not need to go to the formal step of declaring “here is a document on the Web.” Instead, we would just understand that our respective messages continue to be editable — or perhaps contain designated sections that remain editable.
Is that asking too much?