Because of "karma". Since, to truly explain, 'why?', about anything requires knowing the entire history of existence, up to the moment, and humans cannot know all there is to possibly know, karma is used in the East as the appropriate explanation for what we cannot directly know. There is nothing "magical" or "mysterious" about the concept of karma. It is just a shorthand way of saying, "the present is a result of the combined total of the past, influencing the future", which would be a 'cosmic fact'.
In of itself, "wrong" is not life affirming. "Two wrongs only begets more wrong", and cannot make a "right", anymore than "two rights make a wrong". It's just how the universe works. If "two wrongs make a right", "vengeance" would had led humanity to world peace already long ago. Therein lies the inherent contradiction to the question you ask. The idea of "two wrongs" making a "right", likely comes from the relativistic secularism ideology, where "nothing has any inherent meaning, so anything can mean what you want it to mean", which is a fallacy.
By the laws of "attraction" and "equivalent exchange", "karmic payoffs" are a response 'in kind' to an action or decision. This is what The Buddha meant by us not being "punished for our sins", but being 'punished by them'. The Bible and Christianity do not have a specific word for it, but teaches the concept of karma as, "an eye for an eye", and "you reap what you sow". Matthew 7:2 quotes Christ saying, "By the judgment you pass shall be used to judge you, and by the measures you apply shall be used to measure you".
"An eye for an eye", to justify vengeance is a distorted interpretation. Vengeance would only beget vengeance, by 'Universal Law'. 'An eye for an eye', signifies Cosmic Retribution, which ensures the universal balance of nature. Our universe is "holographic", where the 'entire whole' is contained in all of it's parts, and what is seen is dependent on the point of view. Thus, how we regard and frame our world determines what is possible in it, which the Uncertainty Principle explains.