Earlier quoted context omitted.
At which point, the question becomes, "why is this a website?" if you're building an application, usually languages like C#, Objective-C, etc offer far more powerful tools for making an application.
Because a web based application doesn't need installation, it's cross platform and accessible by everybody.
I always thought that the SPA crowd would settle on a custom content-type to handle web apps. That way they aren't hamstrung by the limitations of HTML and web pages and can really do things right by web apps.