@rl_dane All wheels are wobbly, to be honest. And heck, I'm as guilty as the next guy when it comes to reinventing GUI details. In the beginning, Qt was missing some common controls (I think it was things like tabs and comboboxes), and thus the "Linux Widget Project" was born, and then we all went "C++ isn't the optimal OO language, and we can learn so much from NeXtStep/Taligent/OpenDoc etc", rebranded to the "Linux Interface Project"… and quickly succumbed to death by scope creep. At least the GIMP people delivered.
And not having Xt also meant not having the mandatory "X" in there, so porting was assumed to be easier. But I still sometimes picture an era where Xt and its resources would be the common ground, and we'd get a good selection of widget kits you can pick from (or even combine).
As for "sane", I've seen too many Motif 1/Qt/Tk applications where the lack of proper mid-90s widgets lead to some rather interesting design choices…