Why would you want to do this? Because you often don't need more. It's nice to not have to think about your "router" as this big special thing.
Instead, with this approch, your app's current pathname is just another piece of state, just like anything else.
This also means that when doing server-side rendering of a redux app, you can just do:
var app = require('your/redux/app')
var React = require('react')