The social landscape has changed since the early days of messaging. Everybody chats using their real names in an age where saying the wrong thing could mean you lose your job (or worse). People compartmentalize more. Close friends gets one set of thoughts, parents get another set of thoughts, work colleagues get a third. It's easier to compartmentalize with completely separate apps. None of the messaging apps I've ever used (not even tweetdeck) makes managing multiple identities easy. And then there are the network effects of completely disparate social groups...