It does seem like many people lack common sense. Everything from driving, to walking down the street or taking to people, can make you question whether common sense exists. I know it does, seeing as you asked this question. I myself try to practice it but sometimes find myself being unaware or ignorant of things and not always using the best judgement. In some cases I think a lot of people might be overly stimulated or not focused on certain things so it seems that they are being ignorant or have no common sense.