I always wondered why a bunch of different companies make identical graphics cards then complain that it's a horrible business and Nvidia is screwing them. I wondered even more strongly when I saw a dozen flavors of the NVL72 rack. If the rack is so complex and difficult to manufacture, why have N companies do redundant work?
Designing the board is a different business from designing the chip. You're negotiating with the DRAM fabs instead of the logic fabs, selling to a thousand retailers instead of a dozen integrators, etc. And once you've done all that, you do it more than once. ASRock isn't just making Nvidia GPUs, they're making AMD and Intel GPUs, motherboards, wireless routers, etc.
It's more efficient to have companies that specialize in making all kinds of boards than to make each of the companies making chips have to do that too. And it's a competitive market so the margins are low and the chip makers have little incentive to enter it when they can just have someone else do it for little money.
