And they're just as locked-in as Facebook's messenger. If I'm going to switch to something, I'd rather it be something that offers me some tangible benefits over what I currently use. Not being locked in to one company's services would be such a benefit.
Currently I run my own XMPP server and am using yaxim for IM. (Not that I'd expect most people to run their own, it's just easier for me to test things out when I do. :P) It's missing a few things I'm used to, but it's getting there. Always on the lookout for something better though.