It’s odd how that goes. We are never going to subject as many monkeys to coke as people drinking the stuff. So we need to compromise, but rats are not a great model resulting in some false positives. However, presumably some false negatives exist that are silently killing hundreds of thousands of people.
I would like to think that any scientist who dared propose giving to monkeys the equivalent by body mass of the amount of Coca-Cola many humans consume per day would get publicly crucified by an ethics board.
We're running a half-assed trial on the general public right now, only without a defined "normal dose", control group, compensation, or informed consent.