@wowgetoffyourcellphone If you have a group of 20 chariots and you want to make sure those are not in the range of an tower the best thing you can do is adjust the direction. Furthermore you can put units into formations, such as skirmisher. However, formations are nearly unplayable, because you can not decide their direction.
It is not necessary to have any in game bonus by adjusting the direction, it simply gives the human player more control. It is like the feature which allows you to assign groups of units to numbers from 0-9, you press the number and you get the group. This feature gives the human player more control.