Ground speed, though irrelevant to flight, is of great importance when getting into the air in the first place. At takeoff, though indicated airspeed determines when a plane can fly, ground speed determines when it will run out of runway.
Roughly fixed indicated air speed to take off (why it's important). But at ground level, ground speed also important (to how soon you run out of runway). What ground speed is necessary to achieve indicated air speed depends on altitude and temperature (higher and hotter requires higher ground speed to achieve same indicated air speed and this achieve takeoff).
Later, winds of course also affects ground speed necessary to achieve indicated air speed. Why you take off into the wind
