Why is Slack so popular with more than 10 million average daily users?
Slack is bringing hundreds of different work applications under the same roof, enabling companies to use a unified interface for all their communications and data.
While email was built on a one-to-one model of communication where new information was pushed on you, Slack enabled a one-to-many pull model, where anyone can subscribe to any information of interest.
Information in email is only born once an account is opened, and is as good as destroyed once the email account is closed. Meanwhile, Slack enables information to live on forever, so new team members never start with an empty slate, nor is their knowledge lost with transition.