When explaining to children how to cross the street, it's most common to tell them to look left, then right, then left again. This advice also goes for adults, but it's generally assumed that they already know how to do it.
But why is this the standard advice? Some have argued that what you really need to do is look right and then left before crossing. That way, your last check is still toward the cars that would be closest to you. They think that the first look left is useless.
After all, the point of the second look to the left is just in case a car came over a hill, out of a driveway or around a curve while the child was looking right. But, if that's the goal, they could accomplish the same thing by just starting with the check to the right.
The reason to give children this advice is twofold. First off, it makes them slow down and take longer to look at traffic. That's always good. Rushing leads to accidents.
Second, most people in the United States naturally want to check to the left. The worry is that a child who knows they can cross after looking left (in a right/left situation) may forget to check right if they only make two checks. By telling them to do it twice, for three total checks, it ensures that they really remember to look to the right at all.
At the end of the day, safety has to be the focus. As many checks as necessary should be used before crossing a road. Those who still get injured due to inattentive or reckless drivers need to know how to seek compensation.