It has a name... "Nepotism".

I suspect the 'affirmative action' trend also reflects the difference in ambition/drive between the low-income high achievers and the >70% high achievers. The low income group is smaller than the >70% group (look at the size of the 'above average odds' regios and the 'below average odds' regions). This is because most of the people in the low income group will never even apply for a private college -- only the strongest applicants apply. But from the >70% group, basically every kid applies to college, and they are much more comfortable applying for 'reach' colleges (even if it costs their parents a few hundred extra dollars). They've also gamed their test scores.

The pink part is called legacy admissions. It’s how elite universities grow their endowments. That is their ultimate goal: grow and grow and grow some more.

It isn’t just admissions though, it’s also tuition. Schools like Harvard could easily afford to give free tuition to all their students. The fact that they don’t is rather mysterious. I suspect part of the reason is that the students whose families can afford the tuition see it as a sort of conspicuous consumption.