It has the developer sanity that web development lacks with its Frankenstein mixture of HTML, CSS, JavaScript to make <div/> behave like native widgets.
Have you ever tried to use any web design tool capable of matching Blend for UI design?
XAML is what web could have become if XHTML and its sublanguages had been adopted properly.
When I don’t care about the UI design, just need some GUI that works — yes, I still like Windows Forms.
When I have professionally-made UI design on input, and need to make GPU-rendered GUI — XAML is the best technology with the competitors far behind.
Am I the only one who still likes Windows Forms?