The reason is that the company has yet to improve on it for quick and easy desktop development, even though WPF is far superior for scaling, visual transitions and more.
Does WPF actually support turning off font smoothing yet? If it does, then there might finally be a version of WPF that my particular kind of eye problems can tolerate for more than five minutes without giving me a headache.
WPF also seems to give things a rather "written with Visual Basic 3.0" look and feel to me, so I'd rather Microsoft just threw the thing away altogether and we never speak of it again, personally.