Earlier quoted context omitted.
Not to mention SEO. The points outlined above in the top comment (* Caching of shared static HTML for fast-as-possible page loads. * Google indexing and searchability.* Backbone apps that feel more like a series of pages and less like a single-page app.) are all things that Rendr accomplishes that are already taken care of by not making a full blown client-side JS app. I think us developers are running into the same…
It sounds like you are really questioning the usefulness of client-side JS apps in general. Certainly not every app makes sense to be a "single-page app". But if you are creating a single-page app, then why not also allow it to render on the server? I like to think of Rendr as just another Backbone app, that happens to be able to serve HTML from the server as well.
I think I'll understand when I run into the problem Rendr solves...