Parenting in the 21st Century

What has happened to parenting, that a pizza parlor has to post a sign that parents/adults should not leave young children unattended while in the restaurant?  I guess some people have not seen those faces on milk cartons, OR believe their children are so "smart" that they know how to handle themselves when alone in a restaurant.  I even have to remind myself to use my "restaurant voice," and I am well past childhood.