Listen, covering the face is not allowed. The face is for Allah. The face is for prostration, prostrating to Allah and your face or your forehead is to touch the ground for Allah when you pray to Allah especially if you're in Mecca and visiting the Kaaba. Do not cover your face, do not wear a Burqa. It is not the Islamic dress. And you don't have to dress the way others dress. You are your own person with your own style and you are to dress with modesty, with modest clothing and you wear your scarf in a way that's appropriate, elegant and without covering your face.
Those who do, do it out of cultural purposes...its in their culture and think they need to wear that. While in some nations, their women are forced to wear something similar to burqa and its not part of Islam. They are only oppressing others and taking over their minds and individuality. Such as saudi arabia, afghanistan. Only Allah can help them correct the errors of their ways and the difficulties.
some cover their faces because of medical reasons or something happened to their faces.
Allah loves it when you dress with modesty, with beauty especially when you dress your best for Allah. Allah says that you beautify yourself for others but don't forget to beautify yourself for Me.
Prayer is the best time to see Allah when you stand before Allah for prayers. From your personal hygiene, your fragrance, your best beautiful clothes and cleanliness also matters to Allah Azza Wajal
His followers should stand beautifully while taking the prayer for him. Beautify yourself when you take the prayer. Dress nicely when you stand in front of Allah. You beautify yourself with whatever you are able to from beautification in appreciation for the prayer and glorification of the position between yourself and your Lord.