Performance. Which benefits those on low bandwidth. I take it you are aware of offline applications?
Web browsers already do a very good job of optimising content. It's called caching. If the caching mechanism isn't broken by the web server/site then the number of repeat downloads is quite low and this makes it very suitable for slow or low bandwidth connections.
Applications. These are very different to the majority of websites. Offline applications are a great idea, shame about the ball ache of browser compatibility.
Yes, I have heard of the History Web API. It can be useful, however good luck with mobile browsers and many toolkits just don't even support it. Unfortunately because the toolkits don't support it usage is low and then there are the security and privacy problems of history manipulation...
I can take a Stradivarius and play the Paganini capricci on it. The result is guaranteed to be shit. Must be that stupid Stradivarius.
I'm not sure what bearing this analogy has. Could be that many toolkits are poor because they are designed not to enhance basic web functionality (which is accessible and usable) with enhanced features but to instead replace and supplant the basic web functionality? Yes, some toolkits are better than this than others but a great many of them are appalling and cause many usability issues particularly when developers try to enforce desktop application paradigms onto web pages. I still come across copious examples fo dumb developers who want to prevent user's closing browser windows, navigating forwards and backwards through their history or just make reckless and stupid assumptions about screen orientation/space and DPI.
Do you realise that paged (or otherwise filtered) results can be obtained via AJAX methods just as easily as via any other method? It depends purely on the server implementing the appropriate endpoints.
...seems to be a spontaneous rant about something not related to JS at all?
I am sorry, but I get the impression that you are criticising something that you're not very familiar with.
Then comes over that you are clueless and blinkered - sorry if this is wrong but it's the impression I get from this... Create an application using a toolkit that replaces the standard interface objects because you want some "consistent" (consistently awful) user interface? Try to maniuplate the browser windows and interface to delude yourself that your application is running as a rich desktop application and not within a web browser? They're different, plan and design applications differently.