Presently glut chips as an gui for testing and some temporary gui. But,if it is expanded or widended as a complete windowing kit same code can used for different systems(like Java i.e).So,why can’t it be possible??
Because generally developers like do code that part them selves to have more power over it–I would guess.
Not only that, there are portable windowing libraries avaliabe, wxwindows being one of them. And it has functions to create an OpenGL window.