They're not just for African-Americans. There are ones for women, orientals, hispanics, etc.
The rational behind them is the myth that white males are all rich and over-privileged. Thus, if you happen to be a poor white male (such as myself) you'd better get a job really early, rack up some credit (I used a cd-secured loan, which enabled me to get a cell phone in my name, etc. etc.), and then get a whole mess of student loans. My wife on the other hand, benefiting from having two x chromosomes and being just a little worse off financially, got through her undergrad with barely any debt. It was the Vet-school that caught up with her there (because there are no full-ride scholarships for vet-school. They assume everyone is rich).
My basic complaint with this and affirmative action is they are based on racial stereotypes. They assume that minorities and females will have a harder time paying for college, or getting into college, because they assume they're poor. Rather than just assume the Social Economic Status of people, why not make these things based on SES instead?