GUI just doesn't give you the level of control or keyboard driven workflow that CLIs can. You can even use plain kernel terminals or bootloaders if you know CLI. Text config files are also extremely easy to configure. There are only a few legitimate cases where CLI isn't enough. That includes gaming, 2D and 3D graphics design and CAD/CAM. And almost all of them implement their own GUI anyway.
GUI just doesn't give you the level of control or keyboard driven workflow that CLIs can. You can even use plain kernel terminals or bootloaders if you know CLI. Text config files are also extremely easy to configure. There are only a few legitimate cases where CLI isn't enough. That includes gaming, 2D and 3D graphics design and CAD/CAM. And almost all of them implement their own GUI anyway.