Why hasn't the markup language model been popular for visuals outside web design ?

Right now I'm starting to get into WPF, and after working for quite a while at my internship with web design, I find that the markup structure is great for modern applications web or otherwise. I mean most Presentation and GUI framworks are only minimally reliant on the visual aspects and mainly rely on the manipulation of those presentation objects and time is heavily spent in events manipulating them. I find the markup language style much more efficient than what you'd see if you design a site using other GUI frameworks mainly because you can structure the visual aspects much more cleanly and without (on the surface) relying on generation of containers and their children and doing that whole micromanagement just to create a display. I am sure there are cons but with the way most applications are designed for overall usability and clean layouts I don't see that this could be only recently have been utilized for creating applications.

I am not really familiar with markup, but I think XML is widely used for that.

You haven't seen WPF/XAML?

It's a question of whether it will take off. It's not that people haven't tried.

EDIT: Check this out:

http://en.wikipedia.org/wiki/List_of...rkup_languages

That's quite a bit. I would imagine they all share a common sense of simplicity over their imperical models. I mean when I can I would use a RAD tool, but even then it's a matter of having a good tool that translates the many features of the Framework to the tools. With these markup languages, all you seem to need is a markup specification, and since the framework is essentially reading from the markup, the RAD tools would have a very accurate translation between the markup and the final design.

I am really interested in it, A friend of mine is doing a project in it for work, and honestly I thought it was fishy that the web has evolved as it is and no one has decided to capitalize on their model. Guess I spoke too late.

Adobe Flex uses something like this. I found it rather convoluted and more complicated than just specifying in code the positions of controls and objects.

XML is quite commonly used in applications. While its good for online transactions and stuff, I'm not all that big on it for UI layout.

Glade 3 is an visual GUI editor for Gtk that spits out XML documents defining your layout and controls. While its nice to be able to drag and drop widets it ends up spitting out 1000s of lines of XML (I would hate to have to write that all out by hand) and you lose a lot the flexibility you get by coding the interface yourself. As with XML you basically define your own markup language you end up with every app using a different XML based language, which can also be a pain to deal with.

I've used glade. It's handy and you can use the same UI spec across different languages which is pretty handy.