But the main reason is that the topics-based organization and ability for moderators to move/split conversations means one can read and participate in a community much more fully given a fixed amount of time.
Kind of like if each slack thread discussion had a title and was discoverable from the left sidebar and didn’t get in the way of the other threads.
But also, critically, if you want to, you can drop back to the "show me everything sequentially" view. Threads hide discussions away - which is good when you want to focus on something else, but bad when you can't remember where a discussion was.
How accurate is that understanding?