Constantly, for a myriad of reasons. I'm not going to go into it, but all I'm going to say is this:

When you get burnt at a young age on a stovetop, you're going to think thrice about putting your hand on anything that even looks or seems like it works remotely like a stovetop - and when you decide to do it, being burnt again just reinforces to to the point where there's a moment where you find it easier to just skip out on stovetop-like objects than to be burnt again. In the same fashion - as hard on the mind as it can be sometimes, it may be better to hide under the armor and mask than to give ammunition that can (and eventually will) be used against you.

I do it, and to me it makes sense that everyone else does it - because in this world, I find, there's four kinds of people; the people who just don't care about people and have nothing to show under the mask, the people who wear a mask to protect themselves, the people who dare removing their masks and the people who just throw pepper spray or acid at everyone in the face for giggles - and those who happen to not be wearing their masks at that moment get hurt, sometimes permanently (and visibly if they make the mistake of not wearing a mask again)