The Directions module helps you to plan lots of repeated task in a way that minimizes driving.
F.ex. you may have 100 tasks that are planned for an employee in next week, in no particular order, and you want find an efficient way of assigning the tasks to each, to minimize the time spent driving, then you can use the Directions module to suggest the route.
The Directions module cannot handle arbitrary amount of data, the suggested routes start to become useless when you have much more than approx. 100 plannings.