Currently there is far lower proportional representation of low income students in college than of any race targeted by affirmative action. So clearly something

Currently there is far lower proportional representation of low income students in college than of any race targeted by affirmative action. So clearly something isn't working. Low income students are obviously disadvantaged in the admissions process and current affirmative action processes are not remedying it. So the question remains: why shouldn't socioeconomic status be added as a factor for affirmative action?