You can also write shorter programs in assembler than the compiled version of what someone writes in C. The point of Cappuccino (and C) is to manage complexity.
Try writing 280slides in jQuery to see why complexity can be hard to manage.
Try writing 280slides in jQuery to see why complexity can be hard to manage.
That said, once you get to a certain point, the need for further abstraction disappears. Obviously, Lisp-like languages are the epitome of what I'm getting at: as soon as you have powerful macros, you can make the programming for any application trivial by defining a high-level base for it. Domain-specific languages, while typically not as powerful, are also hard to beat, since it doesn't get much easier than, "Put an image with these dimensions <here>."
My point is that jQuery is a powerful enough language (having great abstraction capabilities even if it falls short of Lisp) and HTML and CSS are great DSLs. The combination of the 3 are simply good enough to make defining an entirely new approach a game of diminishing returns.
Of course writing C is more productive than writing assembler. Is writing Cappuccino easier than using jQuery/HTML/CSS? This submission raises the possibility that it is not.
As a developer I'm wary of learning new platforms until I know that I am going to get returns on my new knowledge(skills). We all have limited time, and there are plenty of techniques or popular platforms I could be learning or improving on that I know will make me employable in more situations.
I just don't think your assertion is a slam-dunk. HTML is remarkably good at describing layouts, and HTML+js is remarkably good at making very complex UIs that would take hundreds of lines of code to replicate, even in Cocoa.