What surprises me about that is that I read before that Vitamin C to most animals tastes really bad, but not to primates because we need it to survive. So if losing endogenous Vitamin C production was just a case of "it doesn't hurt", it would mean that primates consumed enough Vitamin C through their diet before losing the ability that it didn't matter, otherwise it would have been a disadvantage, right? But at that point they would have probably disliked the taste.