There is a belief that a face mask is ineffective against the coronavirus, that is a lie. It is true that it is ineffective against the airborne virus. Yet there is another way the virus can be spread, and thus another way to get it. If you touch an infected surface and then touch a mucous membrane on your face, you will also get the virus. There are only a few on your face (people touch their face more often that they realize). These are the eye, nose (nostrils), and mouth. If you touch these with infected hands you can also get infected. How do you prevent touching these. Glasses make it less likely you will touch your eyes. A mask (like the one pictured below) that covers your nose and mouth protects you from touching those two mucous membranes too. Therefore even if you forget to use hand sanitizer (second picture) you can still mostly prevent getting the virus that isn't airborne.
All information is gathered from a practicing doctor.