Why do you need A to do B? Obviously any competent ML practitioner can notice a biased training set. Discriminating against people based on an assumption that race determines ability is just racism.
Are you asking why you can't listen to an employee that doesn't exist?
But more to your point, if these oh-so-competent ML practitioners were doing their jobs right, we wouldn't be having this discussion.
The whole reason diversity is championed in hiring is precisely because a single individual's perspective can only see so far. And if you have a monoculture team who has experienced very similar life circumstances, you end up with the kind of narrow perspective that leads to more racist soap dispensers.
I think I agree with your specific point concerning facial recognition, but not your general point about un-diverse teams being incapable of delivering a good product for a diverse audience. This is because I have recently worked with a team that spent considerable effort on accessibility issues despite none of the team having any disability.
I'm glad that you were able to deliver a product that helped with accessibility, but part of the considerable effort it took was just in trying to understand what someone else's perspective is. It's less efficient than simply having a member of the team with real lived experience that can answer common-sense questions that your team agonized over answering.
And not to say this happened in your case, but even with that considerable effort, it's still very easy to end up with blind spots in your product that a more diverse team would have caught.
It's the same as hiring for any other level of experience for more routine technical skills. If your team has no experience in this area, they'd need to expend a much greater degree of effort to answer questions that someone who is experienced would already have known the answer to.
But more to your point, if these oh-so-competent ML practitioners were doing their jobs right, we wouldn't be having this discussion.
The whole reason diversity is championed in hiring is precisely because a single individual's perspective can only see so far. And if you have a monoculture team who has experienced very similar life circumstances, you end up with the kind of narrow perspective that leads to more racist soap dispensers.