And no matter what, the cards will still only have 16 PCI-E 3.0 lanes to communicate with the CPU, because that is all the CPU physically has. Better to have the cards run in 8x communicating directly with the CPU than to run at 16x with a chip in the middle, especially since no single card can actually saturate a 8x PCI-E 3.0 lane. They're only just barely starting to saturate PCI-E 2.0 8x (equivalent to PCI-E 3.0 4x).