[kls]

I think it really depends on the app. Sure for some apps all you need is some buttons and some input fields. But even in the not so old days of desktop apps we had Authorware, Macromedia Director and HyperCard because some apps are not just data input apps, and this problem existed back then, it was the reason for the afore mentioned application builders if you will.

You mentioned Cocoa and it is funny that you do, because I think that Apple is one of the ones that got it right (I have only done IPhone development, so forgive me if this does not apply to OSX proper). But with the nib file abstracted away from code it allows a designer to build screens, lay them out and then move them on in a work flow to a developer. Allot of the more modern desktop development languages / frameworks now have this separation but it is relatively new and the web seems doomed to follow every incarnation until it too finds that separation of different technologies is the cleanest way to build a system.

The web is a different beast, while there are pure application many of them are hybrids I think Linked-In or Facebook are a really good example of these hybrid application/documents. They are very interactive but at the end of the day they are a document that sums up either my personal or professional life. With them usability and design is just as important as the code that sits behind them.