XUL

Let me get this straight: XUL is Mozilla's cross-platform application development framework. You get to use XML, CSS, and JavaScript for the front end GUI stuff and plain C/C++ for the application logic. Some notable XUL apps are Thunderbird, and its commercial fork, Postbox. Why is it not more popular /prog/?

XML isn't retarded, CSS maybe but as I understand it, you can pretty much ignore it if you don't want to skin your XUL apps, defaulting to the platform's look-and-feel. JS is retarded when it comes to typing but I don't see how you can dismiss it as a language entirely; As a language for scripting GUI events, it does it's job quite nicely and you can still use C/C++ through XULCOM. I'm really puzzled as to why XUL apps isn't more widespread?