Using a socio-economic standard you abstract away the race issue and give an advantage to those who have less money which has a stronger correlation to actually

Using a socio-economic standard you abstract away the race issue and give an advantage to those who have less money which has a stronger correlation to actually having less opportunity. The problem wrt to race and using a socio-economic standard is that there are almost as many whites in poverty as there are black people in total in the USA (~33 million vs ~38 million according to wiki). There is also the issue that even when accounting for socio-economic status, there is still real discrimination (Pager's Discrimination in a Low-Wage Labor Market points out that a white job applicant with a criminal record is more likely to get a job call back than a black job applicant without a criminal record even when qualifications are normalized). Just looking at socio-economic characteristics doesn't solve the problem.