[TuringTest]

> And for a large user base being confronted with this demand "when they just want to send a message" is frustrating.

Isn't it a conceptual framework thing, though?

People have no problem putting a topic when sending emails, and they are perfectly capable of following grouped conversations, as for example in Outlook.

Maybe it would be enough to present it as "a mail application where you can also do chat on a reply thread", to create the right expectations?