There are hundreds of cultures across the world and down the millennia which have designed and used face masks for various reasons. Mostly ritualistic which appeals to facial features that are fixed, but sometimes, and these are my favourite, for costume and partying. The Venetian face mask balls have something of a sinister reputation mostly due to the sinister reputation of the politicians of Italy, but the face mask balls of England were always sites of some daring-do ( e.g. The Scarlet Pimpernel.)
The reasons masks were ever popular is because they allow us to be present and not be quite ourselves, even to the point of not being known at all. There is no society in which the ability to slip out of it is not both refreshing and illuminating at the same time, like taking a short vacation away from oneself. This is a technique well known to therapists and is really the opposite on the face of it, from getting to know yourself better. But actually the two come to same place because by wearing a mask and enjoying its freedom you get to know yourself better.
You get to understand that emotional masks are what help us get through the day and that we have many of then because human beings are not trustworthy. Masks hide us away from others and it takes a discerning observer to see through them to the person and their feelings beneath.