I can't think of any reason these days why a person, male or female, should not be expected to show their face in public. Anyone who does not do so must be suspect. A motorcyclist who did not remove his/her helmet in a petrol station would, rightly, cause an alarm bell to be rung. Custom is no excuse. I do not say 'religion' because the Koran 'only' demands that women dress modestly - it seems to me that it is immodest to draw attention to yourself by dressing so differently to the norm in a Western country.