Why do you need a cloth mask outside on the beach when the transmission outdoors is less than 1%? Unless you are hanging out in line with a buddy that's sick and have been speaking with them for a while, there's no reason for it. The mask does nothing in either case for reducing cases. Same with a factory, because people after a long day are going to socialize. Same with a meat packing plant, because they are stuck together for so long in close quarters and have to talk loudly to be heard. Same with a fishing boat or stable where people sleep on site. Same with residences, where the vast majority of transmissions occur. Same with indoor dining or a movie theatre, where people are going to lower their masks to eat.
Where can they help? Short term exposures like grocery stores and doctor's waiting rooms....not exactly the essential workers they were trying to be assuring for. Or, as you pointed out, greeting a friend quickly less than 6 feet apart or walking side by side, or at the McDonald's drive thru. But the universe of what they can help is very limited. Hence, my guess is that they probably contributed to maybe an overall reduction of 5-15% of cases which otherwise would have happened. Just a guess, but I think it's a pretty good ballpark for what masks alone (not coupled with the moving goalpost of distancing) ends up.