This is the problem - if you have a large user base there is simply no business incentive for federation. It is so much easier (and cheaper) to just build your own silo without worrying about interoperability. Plus you have the ability to monetize a closed system through ads, data mining, etc. There are so many advantages.

And people don't complain (much) because, for chat especially, they have had years of conditioning that leads them to accept (and expect) that communication with their online contacts depends on installing multiple apps from multiple vendors and sharing their data with those vendors on whatever terms the vendors decide.

And don't forget about spam. Spam becomes a problem when your system gets bigger.

Google Talk was, Facebook just had an xmpp gateway.

Google killed the xmpp momentum by gettimg scared of Facebook around 2010. and adopting the 'walled garden' approach.