Inconsiderate? Or lack of common sense?

Driving downtown Pittsburgh is exhausting, no pun intended. Last minute lane shifts and aggressive drivers take so much energy to keep from tailgating in retaliation. While the considerate driver waits to avoid blocking the intersection, the jag off trying to merge jumps in front and blocks everyone else. Is it possible in their past driving experiences they were treated with such indifference? This also makes me wonder: is this nature or nurture? Driver's education should be required for every license issued. Too bad we cannot ask for parent education before every child is born.