The Jitsi guys are currently working on an Android version, let's see what comes out of that.

In general, the reason for the slow adoption of SIP beyond just pure voice telephony is that the SIP/SIMPLE standard with its companions for buddy lists etc. is really crappy, and as a result so are most clients (or the interoperability between them). It doesn't make it better that the mobile device/equipment vendors forked off their own OMA standards, so the situation is pretty bad in that regards.

I still don't give up all hopes to see a proper Android/IOS SIP client supporting voice, video presence etc. while at the same time adhering to the standards.