Trains are relatively long in proportion to their width. That makes the sides of the trains become relatively more important for aerodynamics than the fronts.

Trains are relatively long in proportion to their width. That makes the sides of the trains become relatively more important for aerodynamics than the fronts. Possibly, making the front more aerodynamic has so many disadvantages that it’s not worth it. For example, a train with a long nose means less space for passengers in a given length of train. It also may be a bad choice aerodynamically if you want to have the ability to combine multiple railroad cars into a single train.