1,2,3 is line,
N is neutral
PE is Earth.
Notice that in this system, there is a fault between L2 and the object chassis. If you don't use earth line (PE), the man is dead.
If you use a PE line, the man will only get a voltage of Uf, as indicated in the picture. Uf << UL2 if Zct and RnA are low resistance, a.k.a you tie the midpoint of the generator/transformer directly to ground.
That's how PE saves your life.
Notice in this picture, PE is tied to all nearby conductors to create an equipotential zone. If there is a fault in either the lamp, motor, washing machine, the whole green area increases voltage the same amount. This way, a guy touching the motor and washing machine chassis can survive even in the event of a fault.
Oh and about electronic systems, they are usually low voltage systems, right? It is very unlikely that someone needs protection from their 5V battery powered Arduino. So for almost all electronic circuits, earthing is not necessary.