If masks are worn and used perfectly, they have a very small chance of limiting the spread of a sick person to others. They don't prevent people from catching COVID-19 at all. But the truth is that nobody wears or uses them correctly. Let's assume that the masks completely block the spread of COVID-19 (for sake of argument). That means that all those viruses are now on that mask, since they didn't go into the air. Ever seem somebody adjust their mask while talking, or 6 times while they are talking? Now they have transferred all those germs to their hand and the next door knob they touch is completely infected. Masks do more harm than good.