I agree. There's no reason we can't have this, we've had tools like Delphi and VB for a long time now. Why can't I just choose widgets from a palette and make my own Outlook interface?

Maybe it could even be taken a step further and turn it into a UNIX pipeline composition equivalent in GUI form. Trying to imagine what a system could look like, I see a kind of tiling window manager in which you can place arbitrary widgets (list views, sliders, text entry, etc) and hook together their inputs and outputs, maybe with a little scripting glue.