The problem is the need to regulate only is present because people generally need to blame the system for failure and not them selves.If I am maintaining separation then that implies that I'm making sure that others do the same (or I simply move further away).
A mask isn't a bad idea, in most cases, it's just not a panacea and it may encourage more aggressive behavior. In a crowded place I would use a mask but I would try to avoid a crowded place.
That's hard to do in some countries/cities. It's not hard for me to do where I live however.
If you regulate just for the jerks then they will scream discrimination so they have to impose a regulation across the board.
And it only take one jerk to ruin the planned suppression of the contagion.
I only use my mask when at the supermarket in a confined space and stock on the shelves that could be contaminated by my expectorant. I am not entering any other buildings normally and if I do I wear the mask for the same reasons. However to enforce mask wearing it has to be simple so that the jerk can understand it. If you leave your home wear a mask... simple to understand even for the jerk and easy to enforce.