I don’t think the interviews can be required. But just like SAT Subject tests or AP classes., if they are available and a person does not take advantage of them, that could be a red flag in the application. And if not available, then not having one will not be held against the applicant. A person with no financial hardship can be admitted without taking SAT subject tests, but it is not probable.
If you look up each school’s admissions, they do say “not required” but from 4 Ivy league schools that I just queried, I found “… you will not be at a disadvantage if an interview is not available in your area.” , “encourages you to take advantage” , “offered in-person or virtually” and " Interviews are also evaluative."
My advice to my kid was that is he was going spend time and mental energy to apply, write essays, pay for transcripts and tests, and ask for LOR for a reach school, he needed to do everything he could to give himself the best chance possible.