Look at the pages indexed in google: https://www.google.pt/search?q=inurl%3Ahttp%3A%2F%2Fwww.lear...
Now look at the source with ctrl+u. (example url: view-source:http://www.learn-angular.org/#!/lessons/binding-css-classes)
Now you know why he needs server side rendering (:
Anyway I never tried angular, and this tutorial made me try it. Is explains very very well how to get started, that's true.