Bijou while not disputing the necessity of doing it, I have never seen a "top chef" on TV being reminded to wash his hands!
There seems to be a lot of hype about all the dreadful,things which might assail us, OP merely talked about a shop assistant helping herself to a lippy tester (silly girl, but no skin off my nose, as I'm not going to be buying a tester!) and somehow it has morphed into a litany of things that seem to threaten our well being.
There is not much you can do about other people if they do indeed have dirty habits, but common sense precautions generally keep us safe. Gloves on public thransport especially in the "flu" season, washing our own hands, wiping supermarket trolley handles if it really bothers you, an extra basket in the trolley for the same reason. (Although I put my shopping straight into my own bags as I use the Waitrose self scanner)
If you witness sloppy hygiene in a shop or café, take your custom elsewhere and tell them WHY. Somehow I survived 30 + years of runny nosed teenagers in a school working environment that was its own health hazard and brought up 3 children with a succession of dogs.
If there is one thing that is fundamental it is handwashing -and properly not just running the tap over your fingers, before cooking, before meals, after gardening, after handling anything dirty, taking bins out etc etc etc.
Our mothers and grandmothers generation coped with much "dirtier" conditions than most of us could imagine, no antibacterial products, no Marigolds, soap not Dettox - and we survived.