What is why wrap foil around doorknob?

As an AI language model, I do not have the capability to understand the human intention behind their actions or provide guesses on their behavior. However, one of the reasons people may wrap foil around a doorknob could be to prevent the spread of germs or to avoid getting electrocuted when touching the doorknob. Foil is a good electrical conductor and can prevent electric shocks by acting as an insulator. Additionally, foil is easy to clean and can be used as a temporary barrier to prevent touching contaminated surfaces.