There seems to be a lot of advocacy for tossing everything into the component tree in the React ecosystem - recently I got linked to a snide remark by Ryan Florence on Twitter implicitly arguing for putting everything in the component tree, including constructs that should have a better separation such as routing (which the tweet appeared to be a reference to).
Some services don't belong in JSX though - this is why you have the idea of stores in Flux/Redux/etc. Some data doesn't make sense to couple to the component hierarchy - doing so makes it very easy to create dependencies on the component tree, which decreases modularity, as well as has perf ramifications by increasing the DOM elements that get rendered unnecessarily by React. Some examples are data models, routing, and interactions with non-element DOM api (window.location, XHR, etc.). This also has a side-effect of increasing difficulty of testing what generally should be vanilla constructs not tied to various frameworks/libraries unnecessarily.
