For most people, regular hand washing and not touching your face is orders of magnitude more effective than wearing a mask. But as a society we've become addicted to off-the-shelf solutions rather than boring good habits.
Basic masks can be beneficial for a short time. They need to be replaced at least every hour in order for the benefit to persist. This is routine in a hospital, but is simply impractical for most normal people.
(If a mask stops a droplet containing virus, the virus doesn't disappear. Your own breath and fine droplets keeps the mask material warm and humid—making the mask material great environment for the virus to hang out and spread through the fabric until it can be breathed directly into your lung where it can do the most damage.)
With a disease that spreads while asymptomatic, the droplets we really need to stop are the outgoing ones. A high level of even improper or suboptimal mask usage in the general not-yet-diagnosed population would be very helpful, because it would cut the six-foot proximity hazard zone down to inches.
Basic masks can be beneficial for a short time. They need to be replaced at least every hour in order for the benefit to persist. This is routine in a hospital, but is simply impractical for most normal people.
(If a mask stops a droplet containing virus, the virus doesn't disappear. Your own breath and fine droplets keeps the mask material warm and humid—making the mask material great environment for the virus to hang out and spread through the fabric until it can be breathed directly into your lung where it can do the most damage.)