Yeah, but the point is that some feel it's NOT natural to have so many periods, as we weren't meant to have 12-13 every year. Our bodies naturally would get pregnant often without birth control, skipping MANY periods along the way. Makes sense.
It ties in with the phenomena(?) that women who don't have children tend to have more fibroids and other reproductive issues than those who do.
As for hormone supplementation, I believe there are cases where nature didn't give us all the same, adequate amount...just as we all have different deficiencies from insulin to minerals. If nature erred in this respect, our bodies work better when we have what we need.
It's the SYNTHETIC hormones that cause cancer, etc.