I think the simpler explanation is that the easiest way to have a diversity of thought is through a diverse workforce. We all have different lived experiences, I have many blind spots due to my upbringing. Can I learn these and overcome them? Of course, but it's a lot easier if someone with a different viewpoint is on my team or in my organization.

Diversity of thought isn't just important to cater to a diverse user base, it's important because approaches to problem solving and engineering doesn't have a singular solution.