Let's pretend there is a human somewhere able "to hire the best person for the job every single time". Presumably the best person for the job would be the one

Let's pretend there is a human somewhere able "to hire the best person for the job every single time". Presumably the best person for the job would be the one that maximizes the company's profit. Suppose it's easier to hire the female candidate that's better than all male candidates (hard as that might be to imagine for many on this site) if you currently have a woman working on the team. The existing team of eight high-performing men just isn't as appealing as a team of seven high-performing men and one not quite as high-performing woman.