It's really that simple. It's not about being perfect or 100%. It's only about reducing the rate of transmission of the virus and masks are probably the easiest way to do that.
EDIT: And in terms of mass protests, NYC easily had among the largest protests over the course of a month and saw absolutely no increase in the transmission rate of the virus. Why? Probably because everyone wore masks. So don't blame protests, facts don't back that up.