I'm glad to hear AA is doing this. While most of us are in good health, the use of masks is to protect others. It's nice to see AA taking some responsibility to do what they can to make flying as safe as it can be. Nothing is going to be perfect but at least they are trying.
I've seen a few people post how masks don't protect you. As other's have stated, you are protecting others and if we all wear masks then we are doing everything we can to protect ourselves.
I was sent a funny meme that somewhat puts this into perspective. Thought I'd share:
"If we all run around naked and someone pees on you, you get wet right away. If you are wearing pants, some pee will get through, but not as much. So you are better protected. But if the guy who pees also is wearing pants, the pee stays with him and you do not get wet". Obviously it's not a perfect analogy but it made me laugh and the idea is sound.