Is there actually a significant user base for them though?
I know Messenger was pretty much forced onto users, but other than that I don't know anyone who uses Paper, nor do I think any of my friends will start using Slingshot - especially when there are well established alternatives such as Snapchat.
I'm doubtful many of them have even heard of these new apps, and this is coming from someone relatively young (20 y/o).
Messenger, Paper, Slingshot.
Seems to me that they are trying to increase engagement with the "new" factor. I think it's pretty smart.