I don't know - perhaps because the US RDA guidelines are set for humans and not animals. How much vitamin C does a goat require, and how does that requirement differ from a human being's need? How much vitamin C does a goat get from its normal diet?
Polar bear liver contains many times the RDA of vitamin A - so much, in fact, that the liver is toxic to humans if eaten. The presence of a certain quantity of a vitamin in an animal might not be the best indicator of how much of that vitamin is healthy for us.
In this particular case, humans are quite different than animals and in fact probably need even more.
There are only something like 3 mammal species on the planet that can't make their own vitamin c. Humans and the upper primates, Guinea pigs, fruit bats, and one or two more CANNOT make their own, and get what they need from their diet.
So the amount a goat has in it's blood is what it's OWN BODY made. And it's body isn't gonna make it if it doesn't need it.
And I know about polar bear livers. The fact that a polar bear has that much vitamin A in it's body at all should tell you something about the importance of vitamin A!
Feel free to do some research before you come back and argue.