Why won't chickens hatch if a person has touched the egg with barehands?

They will hatch if touched by bare hands. We raised what is now called "free range" chickens when I was growing up on the farm.

I gather my eggs by hand every day and keep select ones to place under my hens when they become broody. So every one has been handled by hand several times before setting them. Just make sure that your hands are clean and clean the eggs if they are soiled by wiping with a damp cloth and allowing to dry. Store the eggs you want to hatch with the large end up in an egg carton at room temperature.