It's not that they don't know, it's that they don't care. Hot machines go into an attention queue and some tech eventually fixes it. Meanwhile, they serve. As I commented elsewhere, I think it's an effective incentive for software to grow more sophisticated. In fleets that are promptly fixed, there may be a tendency to assume that, for example, all backends are equally suited to receive an RPC. Having a lot of ambient brokenness can be helpful, as Netflix advocates with "chaos monkey".