> AFAIK, the SAT is biased against poorer students, including in its structure, in its content (maybe they've fixed that), and because wealthy test-takers can afford test prep courses.
The idea that the SAT is inherently biased against poorer students is controversial. AFAIK, the evidence for this requires advanced statistical analysis and expert interpretation and isn't widely accepted as definitive. Even among those experts who accept this evidence, there doesn't seem to be any clear sense of what is causing this bias or what can be done about it. It simply isn't the case that the SAT has some glaring bias that can easily be rectified, like questions assuming knowledge of water polo and horseback riding. Student skills in things like reading and math do not exist in a vacuum, but depend on prior exposure and knowledge, which robustly correlates with family/neighborhood/school environment and thus socioeconomic status. Efforts to create tests that are completely independent of those things have not produced useful results.
Quality studies show that the benefit of test prep is modest to moderate, on the order of 30-100 points, and almost all of the benefit is achieved within 8 hours of preparation. Even that benefit is not widely accepted as simply retaking the test can increase scores by 60 points. [1] There is no evidence that expensive private tutoring leads to better outcomes than self-study with free alternatives such as Khan Academy. [2]
> What makes you say that the SAT is the best option for poor applicants?
It's helpful to look at it more as the "least bad" than the "best" -- we need to stop focusing exclusively on the issues with the SAT and think about the actual alternatives. For example, essays, extracurriculars, and prestigious brand-name private school affiliations are all valued by prestigious colleges, and can be bought legally and very easily by rich families. It is much harder to buy a high SAT score. To buy a high SAT score, a family could pay someone to impersonate their child, but this is very risky as the recent Varsity Blues scandal showed.
Suppose we put ourselves in the shoes of a bright-but-poor high school student. We need a way to make ourselves stand out. We can sign up with Khan Academy or download some SAT prep materials at the public library and prepare for a few hours... or we can try to get into an expensive private school, get a private college essay consultant, join a rich-kid sport, take a trip to Africa, and other things that rich kids do to burnish their applications. Which of these seems more practical to you?
If you look at the criticism of the SAT from universities, I think you'll find that they are mostly interested in attacking the SAT in isolation, not comparing with the alternatives. Comparing with the alternatives would require shedding light on their opaque and subjective admissions processes and the way in which those processes favor the rich. On the contrary, research suggests that leveraging standardized tests, and increasing participation in them, tends to open doors for poor students relative to status quo [4][5].
It's interesting that they are so favorable to a change which will make their processes even more subjective and opaque, especially given their history of using subjective and opaque processes to exclude undesirable minorities (yesterday Jews [3], today Asians). Although they have proven themselves untrustworthy, they are not interested in increasing transparency and objectivity of admissions processes. I think we should be hesitant to accept their reports and recommendations as being in completely good faith, given their strong interest in (and consistently observed behavior of) recruiting as wealthy a class as possible each year.
[1] https://slate.com/technology/2019/04/sat-prep-courses-do-the...
[2] https://www.seattletimes.com/explore/special-sections/sat-pr...
[3] https://scholar.harvard.edu/files/dobbin/files/2007_asq_kara...
[4] https://www.nytimes.com/2016/04/10/upshot/why-talented-black...
[5] https://www.nytimes.com/2017/07/14/upshot/how-universal-coll...