I think on TV shows they don't wear them for the same reason that forensic people don't wear masks, surgical caps, etc. It's for show, no one is actually going to eat it. Even if they show them eating cake it's probably not the same one. DId you know that the food that's shown in advertising pictures and in commercials is usually frozen and PAINTED??? Even the shine that makes it look juicy is painted on. And if juice is dripping down it's colored, slightly thicken water.
I was at a Sonic one day and discovered a hair on my burger. There were 4 of us there. When I complained instead of refunding my money they gave me coupons for 4 free meals----yeah, like I'm going to eat there again!