Most of my Raspberry Pis run headless, with no screen. So the image I keep around is Raspbian Lite. It’s half the size of the “full” Raspbian-with-Desktop image, it has everything I usually want, and very little that I don’t.
But sometimes I find I want a GUI.
I don’t want to have to keep the full image around and re-image my Pi. Nor do I want to have to manually install the various components of a desktop environment.
I do want a single command that just “gives me a GUI”.