To the latter question, it's to prevent droplets of spittle from landing on exposed tissue. There are pathogens which spread by droplets, rather than aerosols,

To the latter question, it's to prevent droplets of spittle from landing on exposed tissue. There are pathogens which spread by droplets, rather than aerosols, the Sars2 virus doesn't happen to be one of them. Yes, if you spit directly onto an open wound or mucous tissue, but it doesn't live long on surfaces, and the droplet-fomite route is how that vector of infection works.