Imagine you have two groups of people that have different means and distributions of “input” (could be intelligence, wealth, interests, ...), and this input is somehow correlated with some output (insurance rate, criminality, university acceptance rate). Both input and output are one-dimensional.
Then you only have two choices. (1) You “unify” the distribution and use it as joint input, resulting in one group (the one with the higher mean) getting “more” - many people think this is unfair. (2) Or you can subtract the means first and so make the distributions as equal as possible, which can result in a person from the “more” group having worse outcome than an equivalent person from the “less” group (if the means are close together and the distributions are wide, there will be many such people) - many people would consider this unfair.
There are plenty of examples, current and historical, of society picking one or the other, for different groups and topics: wealth/success/income (old vs young, Jews&Asians vs other Americans, men vs women, whites vs blacks), university acceptance (Jews used to be discriminated against (look up “Jewish problems”), now Asians are, men vs women [1], “positive” discrimination of blacks) - just a few. In many examples historically, we consider (1) fundamentally better than (2) - e.g. discrimination against Jews at universities - but it seems it takes the society a long time to reach this conclusion in each instance.
[1] https://en.wikipedia.org/wiki/Simpson%27s_paradox#UC_Berkele...