I built it, believing it was going to be useful. In the end, it was not. There's no point in keeping unused features around, since the system is just for ourselves.

Since then, we've built a markup language for interface design (GML) which has made GUI development significantly easier, so that's what we're focusing on instead. If someone wants to build a visual design tool on top of GML, they are obviously free to do so, but as with everything else in SerenityOS, people work on what they themselves are interested in. :)