Restaurants are periodically inspected by the Health Department - and if they don't pass, they are shut down. Are TSA areas ever inspected by a Health Department?
For the feet thing - I would be more concerned with a foot fungus than general germs. I wash my hands before I eat, but that's about it. I never even heard of using gloves at the gas station - just wash your hands afterwards. I don't place my purse on the floor. If there is no hook, I just leave it on my shoulder.
I do recall one time (early on in the shoe circus - this was August 2005) my husband and I were flying from Orlando to London. We had heard about the shoe circus, and worn socks (didn't think of bringing an extra pair). Lo and behold - the carpet was freshly washed! How do we know? It was still soaking wet. Now we had lovely wet socks to wear on our transatlantic flight. No other socks available. Couldn't wear those shoes without socks without getting blisters (not good for the start of a vacation). It was disgusting - and there was no warning that the carpet was still wet, either. No sign, no mention.