Like other primates, humans have breasts to feed their young. However, other primates don't have the huge build-up of fat around the breasts which human women go through at puberty. This is because of two reasons.

A. When humans started walking upright (and perhaps conversing face to face more often) it drew attention away from the female's rear end, which until then had been a strong sexual attractor due to its more feminine, round shape.

B. Developing fat around the breasts instead is more noticeable in face-to-face, upright human beings, than the rear end. This is probably why breasts mimic the shape of buttocks. Development of secondary sexual characteristics are also a good indicator of health as well as fertility.

That being said, if young argonians don't nurse, there is little reason for any argonians to have breasts, regardless of birth method. Breasts can be enhanced to mimic buttocks in species where this is desirable to attract mates (which is never the case in reptiles) but without needing breasts to begin with, Argonians should definitely not have them in the first place.