it is a painful for consumers to have to switch in and out of different apps
The Hidden Homescreen
Matt Hartman

There is also a strategic driver. Messaging is where people already are. There are more people in messaging apps than social networks and adoption is still growing. Interacting with people in that environment also holds the promise of being closer to the user, and possibly even forming a more personal relationship with the ‘user’ than we could through an app, email, or website. Clara and Amy are early examples of that potential.