Well, the Pinis are only human and are products of thier times just like the rest of us. I think it's interesting that we can see the evolution of thier thinking as the series progressive. At the beginning thier veiws are pretty conservative, even a little behind the times of when the comic came out.
In the first couple of issues, the gender roles were pretty traditional. The females stayed behind and did not participate on either of the raids on the human party or Sorrow's End. They had to be fetched after Cutter met Suntoucher. It wasn't until issue 5 when Dewshine went to hunt that the issue of gender equality came up.
Recognition was a bond for life, just like a traditional view of marriage. It's not until Blue Mountain where that gets questioned, and even then it still seems to be the assumption. I also get the feeling from issue 5 where Leetah and Savah talk about Recognition that, at the time, even the Pinis didn't see it as the only way of procreating, just the best. So I also had the impression that there were other children in the Sun Village. Of course, we are also given the impression that the Sun Villagers live a LOT longer than the Wolfriders, and the village is not enormous, so it probably would be on the order of every couple of decades that there would be a birth.
Going back to the Cone-head sterility, the story we are told is of the group that decided to stay behind on a dying planet with limited resources and admittedly prefered to remain sexual beings, so it would make sense that if they could use thier magic to make plants grow, they might have been able to magically sterilze themselves, a choice they probably wouldn't reverse when flying through space, visiting possibly hostile worlds.