Even ignoring that diversity can be a goal in and of itself, and ignoring that a lack of diversity can be a useful metric for identifying other problems, there's also plenty of reason to believe that targeting diversity directly can yield performance improvements. If you're building a product for women, you should have some women on your team. If you're building a product for the general population, you'll get better results if your team has a variety of life experiences and viewpoints.

It's the same exact reason why it's good for a CEO to have experience in the industry that they're targeting with their products, and why managers who know at least a little bit about code works tend to do a better job of managing programmers. Perspective and life experiences absolutely help with decision-making processes and can help you avoid certain pitfalls in your product.

Diversity increases your available breadth of input into decisions and planning; it's like the human version of increasing code-coverage in your QA department.