I'm not a "fan", either; but I understand their system and their role in the system, which is more substantial than it may seem to an American.
It's not a belief that their blood has some magical quality; it's more about raising younger royals in the system so that they understand the duties expected of them as they assume their titles in adulthood. It's sort of like cattle breeding, without the prods. They use privileges and perks as prods.
FRiend, I’m no fan of these people or of the Brits in general. They have a barely disguised contempt for us.