The cases where mask-wearers have caught Covid have happened because masks protect OTHERS more than they protect the wearer. If someone wears a mask (that is not N95 quality), but hangs around near other people who are not wearing a mask, they are still at risk. Masks are pretty good at catching virus particles being exhaled by the mask wearer. They are less good at preventing people from inhaling virus particles that have already been spread into the air. This reasoning behind wearing masks has been explained over and over and over.... and it's why we need everyone to wear masks around each other.