Wearing the headscarf is not a requirement of the religion, but a mere cultural belief. Indeed, wearing a headscarf was not tradiitonal in that area in Mohammed's time, but was acquired by conquest. Mohammed himself only reluctantly asked his wives to wear it because his followers felt it was an honour, befitting their exalted status as "beloved of Mohammed". He never intended it to become mandatory for all women. In fact, some say that a wooman wearing a headscarf is claiming to be "beloved of Mohammed" herself, which is practically blasphemy.
So girls who wish to express their piety, or at least their identification with relgion start off with a light scarf. They then move eastward with greater and greater covering, maybe even skipping via indonesia before they arrive at some Gulf state garb of full hijab in the belief that this will make them more fully muslim..
This purloining of various traditions as gradations in piety is ridiculous and mocks both the culture of islam as well as the religion itself. But the leaders don't protest as it is convenient to have the chattels imprison themsleves keep to the Fen Causeway