Common Sense: Why do we need it?

Common Sense:

The Definition - "Sound and Prudent judgment based on a simple perception of the situation and fact."

The Question - Why do we need it?

The Reason - We need them so we do not look like total jackasses. We need them in our daily life, whether it is pertinent or not.

First example, you go to a party, you are having fun, you're drinking and dancing, afterwards you decided to go home and you getting into your car and drive. In this situation, do you...... A) Start the engine and attempt to drive home?, B) Walk home while intoxicated? or C) Start having some common sense by getting out of your car and crash at the house that the party is at? If you picked "C" you are correct, why? It's because if you attempt to drive home while intoxicated you will collide with and inanimate object or collide with a pedestrian and you'll be spending more time in jail or worst state pen for vehicular homicide. Plus, if you walk home intoxicated to you'll will be cited by the police officers.
Second example, you're a amatuer skateboarder and you want to impress the ladies by doing something "big" like grind a 9 stair rail and you haven't done that before. Do you...... A) Just go ahead and do it? or B) Take some practice runs first then go do it? If you chose "B" then you're right, first of all you haven't done something like that before and you need to do some practice runs, but if you sense that something might go wrong then follow your instincts and don't do it.