As for the last reason, because there is still a lot of grease on the surface of chicken feet, these oils will adhere to the finger fingerprints to form a film when eating, which is not easy to remove.
As for whether there are harmful chemicals, no one can say for sure. You must go to a professional institution for inspection, but I want to say that some old brine smells delicious, but those are naturally fermented. Don't kill a century-old soup with a stick. Some of them are really not false names.
Finally, wash your hands quickly, or it will be embarrassing to shake hands with others.