Gyroscopes are required in aircraft. The reason is because it makes them safer. A gyroscope is a device that functions by maintaining its orientation in space. Thus, it cannot be changed when an aircraft turns to its side or flyies upside down.
This makes is safer and less apt to error in case of a problem in the air. The altitude indicator and the device's heading indicator will run when things go wrong. It will runs when the airplane's vacuum pump sucks air inside and the air goes over the blades which, in turn, causes it to spin. It is basically foolproof and that is why it is required on aircraft for navigational purposes. It is safe and extremely effective.