I can't speak for Harvard, but in the vast majority of the world, going to college is strictly on the basis of entrance exams, with some countries also using high school grades, nothing more.
This is done to avoid bias and/or favoritism. I am not an expert in U.S. admissions but my understanding is that they give points for things like whether your parents are alumni or have donated, whether you play sports, whether you were school "president" or other tests of popularity, and a host of things that in my opinion are pretty poor indicators of whether one should be admitted.
High stakes entry-exams have their own problems. Among many other issues, they measure peak performance, rather than sustained performance.
US college admissions have many problems, so don't hear me say they don't need reform, but you are also assuming that academics are the sole thing that college is about. It isn't, at least not in the US. US schools value many things beyond pure academics. Among them being leadership (whether or not you were class president is one such indicator), personal initiative, success against the odds and many other things.
"[T]hey measure peak performance, rather than sustained performance."
I never saw it expressed so succinctly. Excellent!
It captures well the frustration around tech interviews. You might be a very competent worker (sustained performance), but fail miserably during interviews (peak performance). Ideally, you could show a body of work during your interview, but this isn't possible with most commercial software companies. If you are lucky to work on open source for your job, it is easy to show your work.
To manufacture a public body of work for myself, I built two open source projects and published them on GitHub.
(Please do not read that as advice!) I can share and discuss them during interviews.
This is done to avoid bias and/or favoritism. I am not an expert in U.S. admissions but my understanding is that they give points for things like whether your parents are alumni or have donated, whether you play sports, whether you were school "president" or other tests of popularity, and a host of things that in my opinion are pretty poor indicators of whether one should be admitted.