By way of example, Butterfield said that there are about 2,000 messages a day written by humans in Slack at his company. Another 6,000 more are generated automatically by machines. With such a high volume of information, having it all in one place, ordered, highly searchable, and with human chat layered on top helps make a fragmented and overwhelming amount of communication easier to deal with.
Sounds good to me; I wonder if the email zombies will see the light this time.