Who never liked to just sit comfortably while having the keyboard on knees ?
The sing is when it happens you're likely to have an intensive keyboard use and it becomes limited with mouse. Then you probably want to operate your computer with keyboard which begins with being able to reach some "places" or "tools" in the operating system. Of course at the time of DOS it would especially not be a problem but with current GUI OSes, most of the time it is mainly though to be used with a mouse or other pointing device (stylus, finger, ...) but the guys who designed that did not forget those who would not use a mouse and actually, when you master that kind of shortcut it can raise you speed at using your OS or application.
The sing is when it happens you're likely to have an intensive keyboard use and it becomes limited with mouse. Then you probably want to operate your computer with keyboard which begins with being able to reach some "places" or "tools" in the operating system. Of course at the time of DOS it would especially not be a problem but with current GUI OSes, most of the time it is mainly though to be used with a mouse or other pointing device (stylus, finger, ...) but the guys who designed that did not forget those who would not use a mouse and actually, when you master that kind of shortcut it can raise you speed at using your OS or application.