All fair points, but we still have the problem of giving our users a URL to our rich web app which can take them into a node inside a nested state hierarchy. An

All fair points, but we still have the problem of giving our users a URL to our rich web app which can take them into a node inside a nested state hierarchy. And not all applications can be purely server-side. You can't for example build a spreadsheet on the web as a series of request-responses.