Sure. Provide me a realistic way to provide an application across Windows, Linux, OSX, Android, iOS and platforms I haven't even considered with the same codebase (allowing for minor changes to coincide with the cross-platform hacks that go into CSS/JS) and it might be realistic.

But even then, we've still got to deal with the unwillingness of users to install applications versus their total willingness to visit a web page.

So... you're advocating that we roll back the last decade or so of web development.

Good luck with that.

Why not just properly sandbox web apps?

You'd have to give each web page its own sandbox, at which point installing/using it is no more convenient than a native application.

You'd lose portability across platform (OSX, Windows, Linux, each with a variety of browsers).

Except open distribution and being automatically cross platform...

Web pages already have sandboxes.

You're using a web application right now.

You think that's air you're breathing?

Aye, and it would be a much nicer experience if it were native.

Except for everyone who wants to use it outside of the select few OSs for which it would be written.

Web apps are by definition more secure. Well, as secure as the browser, and those are very secure today.