Are you serious? You've obviously never been shocked by a car battery. I don't need to research how much current is passing through my body to know it hurts. Thats the only proof I need. Go outside and get shocked by your car battery and then come tell me you can't feel it.
Not to mention blown fuses, melted wire, possible damage to electronic components. Always disconnect power sources before you do any electrical work. Even something as small as 4v can have impact if shorted.
An associates degree apparently means you invented electricity or some ****.