It matters because when your applicant pool does not approximately reflect the distributions of the target demographic along any dimension, it suggests that you

It matters because when your applicant pool does not approximately reflect the distributions of the target demographic along any dimension, it suggests that you are not reaching the group of candidates you would like to. The qualified candidates are presumably 50/50 male/female, so to see the applicant pool so skewed from that number suggests that the firm is not reaching the full candidate pool it should be. You always want to be reaching as many qualified candidates as you can in order to ensure you are reaching the best potential candidates.