It's amazing and sad for computing that somehow managing to use a sane language to develop software for a very commonly used platform is seen as a serious feat of accomplishment.
C was not designed to create gui's. So its a feat of accomplishment as opening a bottle with your teeth.
IMHO it depends, C/C++ work very nicely with immediate mode UI frameworks, for example nuklear [1], imgui [2]. Though retained mode C/C++ UI frameworks are also quite popular, for example Qt, wxWidgets, GTK.