Well, I'm stuck with using WhatsApp because it's the most popular IM service here in Singapore.
(before that, MSN Messenger was the most popular)
2 foreign friends of mine do use Facebook Messenger, but that's pretty much it. I would rather use LINE, but well... I have to be 'compatible' with my friends in terms of online services. I would have liked to use Google Plus (back in 2011), but all my friends would rather use Facebook, then eventually I got used to that. Maybe it's the simplicity that makes WhatsApp the most popular IM service here.