I remember watching one of the first React demonstrations/talks, and the biggest selling point was literally "You have a web page with various elements, and some of them needs to keep in sync, at Facebook we have chat messages and notifications, and they need to be in sync regardless of where you are, even on the same page, how do you solve that?" and then outlined how having one place for the state to live solves that issue without resorting to two-way data-bindings, instead data only flows in one direction.

Not sure if React isn't being presented as such anymore, but that's still the problem I see React solving, not more, not less.