> Many talented students can't afford or avoid debt in elite universities.
That's actually very very rare. Elite universities will give grants which cover the vast majority of costs for low-income students.
There's a reason the average indebtedness at graduation for Ivies is only a few thousand dollars (and that's not even including the majority who have no debt).
While this is true, many disadvantaged students don't even know this, because they don't even look at these schools in the first place, as they assume they cannot afford to attend. Selection bias.
That means their family is rich and/or has powerful connections. Thus they will be more likely to succeed after graduation.