Skype and Facetime are the mass-market versions. The rest is for hobbyists.

But since you ask, yes, Skype calling on a mobile is still a niche activity, compared to regular calling, because it's not very good.

I say that as someone who does quite a bit of Skype video on mobile.

Skype=hobbyist?

Looks like a minor side-show to me. There probably is a hobbyist demographic that wants to download a client and make ropey VOIP calls, but they are well catered for already.

For the rest of us, stuff that "just works" is interoperable, is reliable, is secure, will do.

Deutsche Telekom, I believe, is backing RCS & VoLTE as its primary IP-based mobile comms services for those reasons.

It'll be interesting to see how, or if, these operator-backed OTT services (TuMe, CleverConnect, etc) become "extensions" of RCS/VoLTE. They are a way to experiment and perhaps build something of a user-base ahead of time. It's better than sitting on your hands.

Maybe they're scared how much more powerful Microsoft could make Skype by integrating it into its Windows 8 OS. That is assuming Windows 8 takes off, which isn't yet certain, of course...

Good point. Desperation, perhaps?  It's amazing really that the big operators haven't developed these services sooner. 

The operators gave Skype much to wide a window to get people on their VoIP OTT service. Why change now?