You never know what's going on with your hands. Even if you wash them every time after using the restroom or shopping, there are still germs that can be transferred to your face and cause breakouts, wrinkles in skin tone (and lines), as well as increase chances of getting sick from a flu virus.
Germs might not seem like much at first glance but they're closely connected to many problems we have today. Disciplining yourself to refrain from touching your face is a difficult task. It's important because it prevents bacteria transfer and acne breakouts, but it also can lead to scarring, premature aging or other serious health problems.