My thinking has always been that of all the possible interventions to reduce viral spread, something like making people wear masks while grocery shopping has almost no negative side effects. Whereas closing the grocery store altogether has major negative side effects, like lost jobs and people not being able to buy groceries.

So I think the evidential bar for requiring masks should be pretty low (unless it is a special case, like making people wear masks when they're exercising likely has larger negative side effects). Who cares if it may not do much? The cost of doing it is so low.

Whereas the evidential bar for policies that do more collateral damage ought to be higher.