I thought of specific examples where this would be useful:
Imagine there are 20 archers standing in one spot. They have a sight range of 15.
But if they were patrolling left-to-right an area of 10 or 20 map spaces, then this would increase their sight range.
When they see the enemy, they start fighting. And because they are patrolling a small area, the other archers in the group would join them in a very short time.
Imagine 3 groups of 20 archers each. Each group about 20 spaces apart. Each group patrols the same area, left-right. If one group engages the enemy, the others are quick to join.
Another more passive example is 10 sticks patrolling in front of 4 bases, where entry points are wide.
In some areas, patrols wouldn't be needed. Where paths are narrow and there is only one entry point, so a single motionless unit is adequate. Other times, patrols would be useful.