The correct answer to this is that the structure of the interface changes over time, and is influenced by the code. If you were to try to implement, say, the interface to HN, then you would create a top bar with some links, a body section, and then a bottom bar with some links. But the interesting part, all the posts, couldn't be drawn in the gui editor, because, well, they are programically generated. You could crea…
I often think, and many agree, that the problem is with reactive interfaces supporting both mobile and desktop. Or that the problem is with GUI editors producing disgusting HTML. And indeed these are both problems. But QTDesigner, and friends don't face these problems. Your GTK app isn't going to be a reactive interface, and QT, not using html, isn't at risk of the "disgusting html" problem. And yet these designers aren't terribly popular either.