Your correct in saying its not neccesarry but its one of the big new features in Premiere. It allows a much faster workflow, for a fairly simple upgrade. Why would you want to hold yourself back and slow down your workflow? In his case unless he has a very slow hard drive its really the only thing it could be. He has a fairly good CPU and a good amount of ram, so its the graphics card in his case slowing down his workflow.
Also if you get into After Effects, you will also be able to utilize the Ray trace render. So really if your going Adobe and want the best, you need to go Nvidia.