There are two piles of applications for your vacancy on your desk.
The first pile is small: those will be the ones to get an interview. The second one is the unsuccessful ones, the ones on their way to the bin.
Now, have another look: let’s say that you disregard age, sex and name and only look at their suitability for the job. Can you honestly say that you have been fair in your initial assessment? Did you assume that because someone is 59 years old they are computer illiterate? Is your waste-paper basket going to consume that female with two degrees and solid experience in your field because you thought that she might need time off to look after children? Or maybe you couldn’t pronounce the name of the very best candidate whose contribution to your company would be way ahead of the pack, so you didn’t consider him.