All of these apps are essentially doing the same things - sending text, pictures, and status notifications. It's a hard sell, but we really need a standard like email or xmpp to allow interoperability.
The value in these companies is the captive audience and the network effect that makes users sticky. There's very little money in producing a commodity chat client (a la Pidgin or Adium).
It is in all of these companies' interests to not work with each other, as their only value is the size and exclusivity of their userbase.
Personally I just SMS now. I'm sick and tired of installing apps just to talk to that one friend who uses it, especially when SMS works just fine.
The only thing XMPP is lacking is marketing. Multi-billion-dollars-level marketing; shouldn't be too hard to do, right ?
A new protocol is needed. In fact, just the other day there was a story on HN where the original creator of XMPP said the same thing: https://news.ycombinator.com/item?id=6849755 The merits of his proposed solution are another matter, though.
[0] http://xmpp.org/extensions/xep-0206.html [1] https://metajack.wordpress.com/2008/07/02/xmpp-is-better-wit...
I don't recall if this made the HN front page, but there was some news this week of interest: http://www.theverge.com/2013/12/4/5173726/you-have-too-many-...
edit: ugh, jer beat me to it by hours