You could stick out your tongue at someone with no one noticing.

You can talk quietly to yourself with no one noticing ;)

You can't suck your thumb either.

If you wear them long enough, your body adapts.

Not a good idea to wear masks too much though because it does lead to minor hypoxia.

Here are some, share more if you have any!

1. Stops germs (coronavirus and others).
2. Saves women money on makeup (no lipstick needed).
3. Facial privacy (You can make faces at people without them knowing! Also, maybe I'm wearing green lipstick, who knows? It's none of your business)!
4. Prevents sunburn (on one area of your face, which causes tan lines, but at least it prevents skin cancer!)
5. Creative styles
6. You can't bite your nails.