Why was the niqab not obligatory for women of previous nations as it was made obligatory for women of the nation of Muhammad (peace be upon him)?

This question is out of place, because the فرض (obligation) of the niqab is not exclusive to the nation of our Prophet Muhammad, peace and blessings be upon him. Rather, it was obligated upon previous nations. A group of Jews still wear the niqab to this day, just as the church saint John Chrysostom believes in the obligation of the niqab for Christian women. The church saint Ambrose also spoke about the hijab in his work: De Virginibus - On Virgins - and his expression therein indicated that he considered it obligatory for all women. The Coptic Orthodox woman throughout her history, until the beginning of the twentieth century, used to wear the hijab.