[everforward]

It's not effective in cases where the disease is neutralized by the environment before you would wash your hands anyways. A lot of diseases can't survive outside the body for long; I think this is more true of viruses than bacteria, but I could be wrong.

E.g. HIV doesn't last long outside the body. By the time blood dries, almost all of the HIV is neutralized.

I think the research has said COVID is similar, and can really only live on a surface for minutes.

Hand washing is great for preventing disease generally. It's less effective against some diseases, but it also has virtually no downsides, so it's still a sane thing to do.