If people say that niqab is important so that man do not gaze at woman, then in today's context, there is gay man who also gaze at man, so by this logic, then man should also cover their face because gay man gazing at man is more problematic and fitna in the framework of Islam than man looking at man.
So the question, what is the function of Niqab, is it prevent man from gazing at woman ?
Hijab حِجَاب is a partition and not an article of clothing. See 7:46, 17:45, 33:53, 42:51. In Surah An-Nur 24:31, Allah tells women not to display their zinah زِينَة which means beautification or decoration 7:31-32. 28:79, 37:6.
The ayah also tells women to cast their khumur خُمُرِ against their juyub جُيُوبِ which could either mean their cleavage or the opening of their garments 27:12, 28:32. Furthermore Allah orders them to pull their jalabib جَلَابِيبِ over themselves 33:59.
So women were told not to display whatever they use to beautify/decorate themselves with, except that which is apparent of it. This has nothing to do with their natural beauty or husn حُسْنُ such as their face.
