It's like wearing seatbelts. Would you have survived your last drive without seatbelts? You probably would've, there were probably no extreme manouvers/accidents that could've hurt you. For I don't know what high-90's percentage of passenger miles driven this day, the seatbelts didn't protect them any extra.
But for the rest of those passenger miles, the ones that did end up in a bad wreck, the seatbelt was probably the difference between life and death. If the wreck was bad enough, some people would still die even with seatbelts on.
The difference between mask and no mask is probably none for a high percentage of wearers (they wore them but they never ran into anyone infected/they didn't get a high enough dose), but if no one wore them, well, statistically there will be more sickness and death.
It's strange how everyone has their own theory about the virus and level of risk comfort. Some think a particle of virus is deadly, others think you need to have a huge viral dose from an infected person to get sick. And whatever you think, you can probably cite an evidence online to back up your conclusion. I'm more of the latter, so I feel secure to be outdoors, but don't make me spend time in a stuffy bar with others in close proximity.