The FPV shows aircraft trajectory with relation to the horizon. It is not vital (per se!) for the handling of the aircraft during takeoff or go around, particularly the performance of the aircraft, to know the trajectory of it as it's not a parameter that helps to manage the vital factors of aerodynamics (pitch and airspeed in this case), which the flight director does brilliantly.
Now, for approach on the other hand, it's quite useful to help to fly that common -3° path...