Some of us (like say, me) are very recent converts to Windows Phone from BlackBerry and perhaps wouldn't mind having a small piece of "home" on board.
Of course people still use BBM, far more tried and tested (and secure) than wide open stuff like Kik or whatsapp. Also, I don't know how its working on other platforms but old school Berry users know that BBM is also a h*ll of a text messaging hub too (you can add regular numbers to it as well for messaging.) No, those numbers won't enjoy the encrypted messaging you have between two BBM users, but for regular SMS it used to be handy for categorizing and backing up SMS conversations as well. But again, on a Berry this is an integrated part of the OS, whereas everyone else, its just another app.
Oh, and BBM for WP is supposed to be in the works:
https://mobile.twitter.com/Blackberr...lackberryScoop For those of you unfamiliar, BerryLeaks is a mighty reliable source for the obvious; information leaks with regards to BlackBerry, and they're relatively respected because they're not often wrong or far from the mark.