It's more about breaking up a monoculture. You can't introduce a representation of every possible division of humankind. But that's an unrealistic extreme, just like having no representation is an extreme. At some point, working in a diverse environment you just start thinking about others more than before.
Random example I've seen many times, but feel free to extrapolate to other positions/issues: If you have a group of native British developers of a web app, there's a good chance that any non-latin input will be either mishandled or rejected. Not because they hate other languages, but simply because that's not a problem they run into, or think about. Add one (for example) Greek dev, and the team will be quickly made aware of and learn about the locales and encoding issues. This will help the accessibility for all cultures, not just British and Greek.
Exposure to enough people different than you makes you think about others more. Even if you don't work with every possible token representation of the difference.
