The key concept taught is Voltage vs. Resistance.
Voltage is the "Push" (Water Pressure): A car battery only has 12 Volts of pressure. This is very low.
Resistance is the Opposing Force (Friction): Your dry skin has a very high electrical resistance.
Result: 12 Volts of pressure is not strong enough to "push" enough current through your body’s natural resistance to cause a shock that will stop your heart or damage your tissues.