Except there is no convincing evidence that they actually do help others, and the whole theoretical mechanism is centered around catching large respiratory droplets which is at odd with the totality of evidence pointing towards aerosol being the dominant mode. I would add if droplet transmission is the dominant mode, which I very much doubt, then masks would still fail in a real-world setting when you look at the fact they make conversational partners stand closer or speak louder, and the massive cross contamination that happens to almost everybody wearing these pieces of cloth over their faces (hands touch mask, mask touches hands, etc)