Because it's paraphrasing from the Law of Nations. Second, I believe this court was taking a stand against the 14th amendment becoming too broad. They make a very fine point of how natural-born citizens don't need the amendment neither before nor SINCE it was adopted. Third, they are recognizing that the various states had different citizenship rules of which there was doubt, but that for persons who fit the characterization of natural-born citizen, there is no doubt. In effect, they're saying that the characterization of natural-born citizenship means citizenship WITHOUT doubts. As we learned in Wong Kim Ark, the 14th amendment carries plenty of doubts that have to be reconciled. This decision did so by using permanent residence and domicil to satisfy the subject clause of the 14th amendment, thereby limiting it's impact to the children or resident aliens, which Obama does not fit, same as he does not fit the natural-born citizen definition.
Otherwise, what point did it serve the Minor court to say ANYTHING about the parents being citizens unless it was used to exclusively define natural-born citizenship?? This is the question that Foggers and Faithers can't answer without admitting that citizen parents were used to define natural-born citiznes. I don't find this vague at all. The Minor court explored every other way to become a citizen including naturalization (which is also part of the 14th amendment), but the court only characterized one set of circumstances as natural-born ... those persons born to citizen parents. If it could mean something else, they would have said so, especially considering that Minor argued she was a 14th amendment citizen. All the court had to do was accept that argument, but they did not do so.
Perhaps you are speaking above my head but to me, it is not very clear or complete. In this case (Minor v Happersatt) no one was arguing that Minor was not a citizen. The distinction between a regular citizen and a natural born citizen was not even an issue. Everyone agreed she was a citizen. The reason for her action was simply her gender. She was being denied the right to vote because she was a female.
The courts remark saying that it was never doubted that children born of parents who are citizen are themselves natural born, points us in the right direction but is more like a passing remark (obiter dictum) because it is not central to the actual case.
I maintain that we need a clear spicific definition. ....
example
A Natural Born Citizen Can ONLY be a child born of 2 U.S citizen parents who are subject only to the laws of the United States and not subject to any foreign authority or hold any foreign allegiance etc .... etc
Relying on Minor to come to the above conclusion is a mistake. Sorry, I just do not think Minor is a strong enough precedent.