I have been wearing a mask most of the weekday for the past ten years. I love them. So many advantages.
Mitigates my bad breath.
Don't have to fake a smile.
Vice versa, can grin while listening to a podcast on the bus without looking like a murderer.
Has a general connotation here of "leave me alone" anyway.
I have a stuffy nose but I feel self conscious mouth breathing when walking up a hill or something because I am out of shape. With the mask nobody can see that.
Similarly, yawning openly
This is all outside of health concerns for others and myself. It would be easier to list downsides because I can only think of one, they can be uncomfortable/hot depending on the brand. Also, now that everyone has to wear one, I find it hard to remember the names of new people and I think it is partially because I don't really know what they look like. Apart from that, yay masks!