Why do the SAs and the vast majority of civilian college require SAT scores if they are so flawed? Evidently SAT scores are just fine until they don't tell you what you want to hear. Maybe we could use the SAT scores from just the non-URM candidates and evaluate the URM candidates on leadership potential instead. Oh wait.....
Good Question - they require them because it's basically the only game in town.
The bias on the SAT is very well documented. Even elite colleges have recognized this and will consider many other factors besides the SAT.
The SAT (and to a lesser extent the ACT) are the only nationwide tests given to high school students to assess aptitude or achievement.
It is impossible to compare GPA's and even transcripts because they vary so widely. This is why admissions uses a combination of factors - they want to know the ability candidates have to do academic work and how they stack up against their peers. They also want to know what classwork they have attempted and how well they did.
Clearly, if you get a 700 on the Math SAT, this demonstrates that you have the ability to handle college level Math - Calculus and higher.
However if you score a 550, then you need to bring other evidence of ability to the table - coursework and grades.
Admissions is very well versed in the ethnic and socio-economic bias of the SAT. In fact, the College Board (the company who makes the test) admits this and publishes very comprehensive data on this each year.
The College Board urges admissions offices not to use the SAT solely to make an admission decision.