I have finally figured out why Argonian females have briasts. Argonians are Monotremes.
Montremes are mammals that lay eggs and secrete milk.
Platypus and Echidna are examples of the two remaining species of Monotremes on earth.
Platypus lay eggs, spend all their time in water and have a duck like bill. The duck like bill on a platypus is able to sense electrical fields of other organisms. Scientists say that Dinosaurs became birds. Argonians are lizard-like. Therefore I conclude that Argonians are an early form of Monotremes, as evidenced by the feathers they have on some Argonians.