Here is a question for you all. When a train has two locomotives, the first is obviously facing forward. Why does the second usually face the rear? I am sure you knew the answer almost before I asked.
Goofy Answer:
So that set of locomotives can be connected to either end of a train and there will be a control cab in front for the engineer. The locomotives do not need to be turned around before going in the opposite direction on a different train.
Howsomever, in the days of steam both engines faced the same direction and required full crews in both locomotives, which had to be turned around on a turntable or wye before they could be used on a train going in the opposite direction.
It depends on what the terminal facilities are as well - some have the ability to turn engines, or simply have enough locomotives that they can just pick what they want.