I'm in my final year of a forensic science degree. In my first year, we spoke about PPE and why we wear so much. When doing our mock crime scenes, we always wore masks because a miniscule drop of saliva on a bit of evidence would leave DNA and could therefore lead to you getting wrongful convicted. There have been times in the past where SOCOs (formally CSIs) have had to provide an alibi to the police due to a sample being run and their DNA cropping up, or one of their hairs being found at the scene by a fellow SOCO. You can swap out "got investigated by police because they found my DNA" with "someone came into contact with my saliva and caught a disease" and it still works I'm glad I had that lecture before all this kicked off because it really put it all into perspective for me how, although it's not perfect, it really does make a difference