To do manpower projections.

In my case I have a production pipeline for a 3D computer game. Lets say I need to build 50 3D monsters. Each monster is modeled, textured, rigged, and animated. Each of those 4 steps is done by a different type of artist each costing a different amount based on their skillset. I can represent the building of one monster as a task with four sub-tasks. I can also replicate the task (and sub-tasks) 50 times in the timeline and play games with developing the tasks in parallel to reduce the time to make all 50. When I do this the Resource Graph will show me where I am over allocating the different types of artist and i can estimate how many to hire. However, if I want to play games with the resource allocations then I have to edit each of the 50 tasks and associated sub-tasks rather than change them in one spot.

You will probably tell me to use Excel...