Right, because people definitely read each thread in emails and definitely don't read each message in a thread. It's incredibly easy to link to a specific point in time in Slack, where you can contextually read the discussion from there. Quoting email replies is not the same.

> most people

Based on what number of people in what context?

To put it another way, I don't go back very far when opening an email. Slack, on the other hand, I make sure to read each message.