The purpose of the benchmark is to find out what hashrate your hardware is capable of with each algorithm in order for the auto profit switching feature to function. Without benchmarking the hardware that feature can't function since it has no data to base it's calculations off of.
Yeah, but if I have 8 identical cards, NH insists in running the benchmark on each of the individually. I wonder why there is no option to tell it to only run the benchmark in the 1st card. I wonder if it could have anything to do with the fact that when you benchmark, all the hash goes to an internal NH address and not the one you have defined in the client...