N95s don't stop viruses either.
The common misconception is that the mask is to help you not get it. The real point is to help not spread it.The face covering helps stop the spread by preventing an infected person from aerosolizing it via droplets in coughs and sneezes etc.
With that said, any mask is better than no mask as it can also capture droplets and help prevent it from entering. Although if we really want to be effective we'd all need a mask like the asian countries that are used to battling SARs and MERs