Hijab is definitely a religious wear, but as for niqab and poshia, one of the reasons girls do wear abaya with headscarf ( niqab, poshia) is that it gives them a sense of protection from unnecessary attention from men.

I can assure you that many non-arabic and non-muslim women here do wear abaya and hijab if they have to go alone somewhere in Doha.

In the western world we are not used to harassing women on the streets, therefore no need to "fend off".