I used to think that too and even began to write something like that. But what happens if something important accidentally is discussed on the chat? Right, someone has to move it to the sticky "forum" part of the app. That is complicated.
I'm sure it's not dead simple, but that doesn't mean it's worse by any stretch.
On further thought I wonder how much of the problem I have with slack and similar services (of which I actually tangentially happen to work on one) is more of a problem with process and expectations than anything else.
1. You are expected to be on chat, otherwise you suffer the appearance of not working - counter-productive since you are now subject to distracting notifications. If do-not-disturb settings and turning off notifications wasn't frowned upon this might be less of an issue.
2. Important information should be distributed through a more persistent second channel, email or a web-viewable email-list may actually be suitable.
