That is a good point which is worth discussing. From an opposite point of view Czech Republic mandated masks early on which seemed to work. Now they are in a bad state which is being blamed on relaxing the restrictions they had in place.
Hypothesis: Wearing a mask is a physical reminder that we're in a pandemic, which helps folks remember to do other things which reduce their risk (avoid touching things unnecessarily, wash hands more often, staying at home unless necessary, etc)