If I want cow's milk to have more of those things I can simply reduce it. But often cow's milk has too many of those things, so often it's used in other things. Hence, if you had a diet of only cow's milk and no water, you would end up fat. So it doesn't matter how rich it is in those things. If it were richer than cow's milk in those things it still wouldn't make it better than cow's milk because there is no fixed richness that is better than another. One quality that cow's milk has that cockroach milk will never have is that it isn't from a cockroach.