Yes, I know they don't travel through your skin, but once they get one your skin, you can transfer it to open areas of your body where it can enter the body. Masses of people touching the same surface spreads germs. You can avoid getting sick by careful washing, etc, but it's better to just wear some shoes (I hope you will not be washing your feet in the sink in the parks). Your feet are going to be sweating and leaving sweat prints on the floor, and probably not smell that great either. They're going to be covered in dirt, and god knows what else. It's just plain gross, and rude. No one wants to see your stinky, ugly, dirty feet. I can't believe someone has to explain this. I am not concerned with etiquette for the most past, but geez, we have to have some standards, or we might as well be cave men.