I mean surely its an obvious one, if everyone is the same, with the same views, values, attitudes and skills doesn't that make for a much more limited workforce?

Yes, so why does it happen? 

Well lots of reasons and some are unavoidable such as the location you can recruit from and also the skill set you may need but there are also other factors like culture, management and leadership capabilities and yes, sometimes prejudice.

 I have been involved a number of conversations about how to manage a more diverse workforce and it can often come back to a shift in culture but the skills aren't complicated. 

Lets learn about the individual, the person, their motivators and their unique perspectives -  and reading this article it seems to be worth it.