Well, for one thing, as I understand PA has some pretty strict homeschooling guidelines which may limit your choices or methods. As I understand you guys have a fair amount of reporting to do. In Texas, we have virtually no regulation. We do not have to report to anyone, show any records, have curriculum approved, or take state tests. Maybe the other methods are more compatible to your state's requirements, and that's why they are more well known.
Also, I think CM is more popular among conservative Christian home-schoolers, although I do know of Jewish and agnostic homeschooling families that use it. Our only large homeschool group is faith based, and outside of one very small group aimed toward young children, there are no organized secular groups in town.
In my circles Well Trained Mind, Charlotte Mason, and Classical Education are well known and popular.
What other methods do you hear about most where you live?