Why is this the one time someone is expected to disprove a claim rather than the claimant being expected to provide evidence? If you're making the claim you ne

Why is this the one time someone is expected to disprove a claim rather than the claimant being expected to provide evidence? If you're making the claim you need to provide the evidence. Most people would say that a persistent disparity means it's possible there is discrimination, but it's not definitive proof.