If you are in a lockdown, you are not going anywhere, so you are unlikely to be wearing a mask.
That would be curfew, not lockdown.
It doesn't surprise me in the least. I doubt there is very much reliable data about mask usage in the real world. For example, does anyone know the percentage of people who wear masks in jurisdictions with a mask mandate and the percentage of people who wear masks in jurisdictions without a mask mandate?
I have not been in the States during the pandemic, so can't comment on that, except that my daughter, in her capacity as a gym personal trainer in Miami, has to wear them (and her class) during a very, very strenuous hour of exercise.
But here, in Belgrade, I would say, based on personal observation, that 90+% of people have been wearing them where required, and many where it is not required (e.g., outside). And yet, there is a spike in recent days.