Earlier quoted context omitted.
My guess is that the US used to have objective criteria but because University admissions are so competitive everyone studied just for the test and Universities filled with people who were very good at "book-learning" at the expense of everything else. They wanted students to be more varied, more well-rounded individuals instead of robots who memorize books. So naturally, they started testing for holistic well-rounde…
I always thought it was so they could reject undesirables (wrong ancestry and such) without having to give the real reason.
Now they are probably using the subjective tests to attract disadvantaged minorities.