So, as a people we default back to hiring people who look like us, think like us, and act like us, even if that isn't representative of the larger population, and even if it restricts the population of people who are likely to be perfectly qualified, given the chance. Keep the playing field tilted towards "us", whoever that may be in the given situation.
And it just so happens that with our enlightenment we exclude the people who have always been excluded. A funny coincidence how we keep coming up with that same solution, rather than challenging our own assumptions as lazy mammals.