Facebook nixes access to chats outside of Messenger walled garden

The push to separate apps for everything is so gross. I use Paper instead of the main Facebook app on my phone because though it is rarely updated and lacking many new features, it has integrated messaging. Even then, I am often relegated to the mobile site. (For instance, Paper chews up tons of LTE bandwidth if allowed, so I only use it on wifi.)

I don't understand what their endgame is. More advertising dollars? Less work for developers? Monopolizing more of users' time and storage space? It's baffling.