Both points are true. Think about having giant holes in the sidewalk. On the one hand, if you walk into a giant hole in the sidewalk in broad daylight, that's p

Both points are true. Think about having giant holes in the sidewalk. On the one hand, if you walk into a giant hole in the sidewalk in broad daylight, that's pretty much your fault, and your friends will laugh at you. On the other hand, everyone understands that some people will inevitably walk into a giant hole in the sidewalk if it's there, and so we consider it negligent to dig one without putting up bright orange barriers around it. In part that's because some people are more vulnerable than others (maybe it's nighttime, maybe their eyesight isn't very good, maybe they're going fast on a bicycle), and in part that's because with a large enough group of people some of them are bound to be careless, distracted, or unlucky.