Aerodynamics don't play a major role in semi high speed operations upto 160-180 kmph, since the drag is ignorable at such low velocities. Beyond 200 kmph, aerodynamic properties must be taken into consideration as drag plays a significant role.
As of now, only 4 or 5 WAP-5 Locos are allowed to touch 160 kmph with Gatimaan, hence no need to make them aerodynamic.